Sega's SVP Chip: The Road not Taken? [Archive]

Joe Redifer

03-17-2006, 01:32 AM

Pretty good article. Virtua Racing is an awesome game, but was poorly ported for the SVP version. The 32X version DESTROYS it (and the Saturn version) in every way. I do take exception to one of the comments in the artcle, though:

According to a former Genesis programmer, the genesis [sic] had a great deal of limitations on the number of colors it could display onscreen. Programmers were stuck choosing from four palettes of sixty-four colors each, and could only display sprites that used sixteen or fewer of these. Many games used tricks that would allow programmers to switch palettes part of the way through drawing the screen (this is how Sonic the Hedgehog could have a bluish palette underwater coexisting with the brighter colors above) but these kinds of tricks could only do so much.

That must have been one hell of a poor programmer. What he is basically saying is that the Genesis had a pallette of 256 colors and could put 16 onscreen at once. Bullshit. Complete and utter bullshit. The Genesis had 512 colors, 61 of them could be onscreen at once, but sprites could only be assigned 16 colors per block. Sonic is no technical feat for the Genesis as far as color is concerned, that's for sure.

However the SVP Virtua Racing looks pretty bad. It is obviously using something similar to a Master System pallete. It is quite obvious that only 16 colors may be onscreen at once and only 64 total colors are even accessible. I blame either the SVP itself or the programmers inability to deal with it... most likely the SVP. The Genesis definitely had far better colors than SVP Virtua Racing displayed, as seen in the very first games released for the system. Also, the sound in that game was pretty bad. If the SVP provided any enhanced sound capabilities, it sure wasn't used in that game. The game also did not scale or rotate any sprites.

I find it humorous how no emulator (that I know of) can run SVP Virtua Racing. I should do a feature comparing and contrasting this and the 32X version since I have them both. In short, the 32X version blows it away by a factor of about 100.

segagamer

03-17-2006, 01:03 PM

That may explain the reason for Sega not using the SVP chip to bring Virtua Fighter to the Genesis.

Melf

03-17-2006, 04:17 PM

Pretty good article. Virtua Racing is an awesome game, but was poorly ported for the SVP version. The 32X version DESTROYS it (and the Saturn version) in every way. I do take exception to one of the comments in the artcle, though:

That must have been one hell of a poor programmer. What he is basically saying is that the Genesis had a pallette of 256 colors and could put 16 onscreen at once. Bullshit. Complete and utter bullshit. The Genesis had 512 colors, 61 of them could be onscreen at once, but sprites could only be assigned 16 colors per block. Sonic is no technical feat for the Genesis as far as color is concerned, that's for sure.
Nope, that's my bad. I misinterpreted what he said. Here's his exact quote:

The primary limitation was that the Genesis graphics hardware used to access the screen could only hold 64k of graphics data, which wasn't enough to render the whole screen as individual characters. And, of course, the Genesis hardware could only display 512 colors, in 16 color characters, choosing from only 4 color palettes. The SVP may have been able to do some heavy interrupt processing to simulate a true 512 color mode, but it seems unlikely to be used in that fashion.

I fixed that in the article. :)

Mel

03-17-2006, 05:23 PM

Nope, that's my bad. I misinterpreted what he said. Here's his exact quote:

The primary limitation was that the Genesis graphics hardware used to access the screen could only hold 64k of graphics data, which wasn't enough to render the whole screen as individual characters. And, of course, the Genesis hardware could only display 512 colors, in 16 color characters, choosing from only 4 color palettes. The SVP may have been able to do some heavy interrupt processing to simulate a true 512 color mode, but it seems unlikely to be used in that fashion.

I fixed that in the article. :)

That's some mighty technical stuff right there. Too bad no one has put together a relatively easy to understand sdk otherwise we'd have a bigger network of homebrews comin' out.

I suspect the majority of the code on the Genny was done in Assembly.

David J.

03-17-2006, 10:37 PM

Actually, no emulator supports Genesis Virtua Racing due to a lack of good emulation on the SVP chip.

Flash1087

03-17-2006, 11:38 PM

Very well done article here, sirs. Wonder who this 'mystery programmer' was?

Melf

03-18-2006, 01:01 PM

Thanks. He's a reliable source, trust me, but wanted to remain nameless due to possible conflicts of interest. He's probably the most knowledgeable person around on the SVP.

Coicidentally, this is my 100th article for Sega-16, since I had to push back the Data East installment of Lost in the Arcade. :)

Zebbe

03-18-2006, 01:21 PM

Very informative and well-written article. I guess Virtua Racing doesn't work on the 32X because both the game and the add-on has a SVP.

j_factor

03-18-2006, 04:17 PM

ary incorparated

03-18-2006, 05:04 PM

Yup J factor is right,Genesis did that by its time,it surpassed snes ehy,vectorman,redzone,Phantasy star 4,Panorama cotton,and yup some sega cd titles for that reason.Batman returns,Batman and robin,silpheed soul star.All running on stock genesis hardware and pallet,so consider snes blown away unnoticed,cause much of those titles are a bit unfamillair to the standart gamer ehy.

Ro Nova

03-18-2006, 05:13 PM

I like what Mr. Hawkins said about the confusing message Sega sent to their customers regarding what hardware to buy. It must have been very difficult to make a decision back then. Should I stay put or go for the upgrade? What factor did some games play in the decision of what Sega consoles you just “had to have”? When the Genesis, 32X and Saturn versions of Virtua Racing were released didn't it mean that each game was in competition with each other to some degree? I'm not sure of years but I am assuming that the three versions were released fairly closely of one another. The Saturn came out in 1995 and according to TRST data (what is that anyway?) 64% of games being sold that year were 16 bit. Did Saturn’s version come out around this time and weren’t the Genesis and 32X versions already on store shelves? I'm going to stop now because my head is going to explode.
Great article as usual Ken.

Melf

03-18-2006, 05:19 PM

Well-written article, but I disagree with its premise. 32x vs. SVP needn't be an either/or thing. Really, they didn't need either of them. All they did was draw attention away from the stock Genesis and Sega CD games; there was some pretty impressive stuff coming out in that time, and Genesis could've held its own. What would've really saved them is less unfocused marketing, and playing up games like Dynamite Headdy, Red Zone, Ecco 2, Soul Star, etc.

Hmm, I see where you're coming from but don't know if that would have been enough. I mean, if the SNES, which was loaded with all kinds of hardware feauure goodies, was already turning to chips for extra power (other games used them too, like the Mega Man X series and Yoshi's Island), then the stock Genesis would have looked pretty old pretty fast.

Basically, embracing this chip would have meant that Sega would have followed the same road Nintendo did: keep gamers happy with excellent software (which they did, with the games you mentioned), but at the same time keep them hooked for the next gen by offering a taste of what more powerful consoles could do. Nintendo did this by using the FX chips and sticking with the SNES until '96. It paid off big time for them, and their only real flaw was going with cartridges for the N64.

Had Sega done the same, they may have maintained enough of their user base to have made the Saturn a true contender in the U.S. I don't think the stock Genesis could have done this all by itself (and we know just how well the hardware features of the Sega CD were being used).

Zebbe

03-18-2006, 05:46 PM

Well said Melf, but Nintendo had another big flaw: the Virtual Boy.

I'm a little bit against chips, since it's like doping the console. I'm more impressed by seeing for example Sonic top speeding in Sonic 2 than the polygons of Virtua Racing, since it's something the G/MD can do on its own.

j_factor

03-19-2006, 01:30 AM

Hmm, I see where you're coming from but don't know if that would have been enough. I mean, if the SNES, which was loaded with all kinds of hardware feauure goodies, was already turning to chips for extra power (other games used them too, like the Mega Man X series and Yoshi's Island), then the stock Genesis would have looked pretty old pretty fast.

Hmm, I still disagree. SNES used chips in its games from Day One -- F-Zero and PilotWings, launch games, had chips. SNES had a very weak processor, and as such was more in need of coprocessors. Ever notice how Mode 7 doesn't look so hot on games without a chip?

Sure, stock Genesis hardware couldn't have done Virtua Racing or anything to compete with, say, Star Fox, but that's not necessarily a huge loss. Sometimes you concede a battle to win the war.

Basically, embracing this chip would have meant that Sega would have followed the same road Nintendo did: keep gamers happy with excellent software (which they did, with the games you mentioned), but at the same time keep them hooked for the next gen by offering a taste of what more powerful consoles could do.

I would say that Sega's version of doing this was the Sega CD (which arguably does more for that than Super FX does). And perhaps if Sega hadn't left Sega CD in a ditch in 1994, more people would've seen it that way.

The games that I mentioned, I didn't mention just because they're good games. I mentioned them for their visuals, and I think those games (along with some others like Contra Hard Corps) showed improvement over the previous year's and proved that Genesis had potential that hadn't been tapped before. Ecco 2 certainly didn't look old at the time.

Nintendo did this by using the FX chips and sticking with the SNES until '96. It paid off big time for them, and their only real flaw was going with cartridges for the N64.

Did it really pay off for them? It paid off for SNES, but maybe not so much for N64. N64's obstacles are numerous -- its late release, its lack of games, its use of carts as you said, its lack of third party support, and more. It's practically a miracle that N64 was as successful as it was, and it only was because it had a few games that really caught on in a big way (plus Sega killing itself to give N64 more room).

But I'm digressing. SNES was indeed the #1 selling system of late '94 and all of '95. I think it could've been Genesis instead, if 32x never came out and Sega hadn't said they were ousting Genesis in 1995.

I think you're giving too much credit to the chips. SNES had games with chips for three years while remaining consistently in second place. It only overtook Genesis in 1994 because Sega failed to promote Genesis and its games anymore in 1994. It was Sega's market to lose, and they practically handed it over on a silver platter.

Had Sega done the same, they may have maintained enough of their user base to have made the Saturn a true contender in the U.S. I don't think the stock Genesis could have done this all by itself (and we know just how well the hardware features of the Sega CD were being used).

Saturn could've been a true contender in the US despite anything that happened to Genesis if Sega hadn't dropped the ball with that "pre-launch launch" crap, and initial high pricing, and questionable choices of what games to keep in Japan (like 3/4 of the games that made/kept it popular in Japan were only released in Japan), and weird spacing of releases (nothing special for a whole month, then several key titles in the same week), and lackluster marketing, and so on and so forth.

I mean, Mega Drive didn't exactly have a great userbase in Japan, but Saturn was still able to be the #1 console for a while.

Joe Redifer

03-19-2006, 01:20 PM

ary incorparated

03-25-2006, 07:15 PM

i think pretty good joe.but ehy super street fighter came packed with round 40 megs,didnt it.i dont know what the use of that upgraded cartridge was,i actually think it didnt need the extra limit to pull it out a genesis,i can name much more nicer games for the genesis.

if snes could run it on its stock hardware then the genesis version didnt actually needed so many memory extra,thrown away memory okay if it was like a street fighter alpha game,then they needed them.

ary incorparated

08-20-2006, 08:36 PM

Man,maybe Just a extra processor could do it for the genesis ive seen what the, stock genesis was capable of Batman and robin Gunstar the tsuf whas already in,maybe for the fun a little sound boost like 2 or 3 sound channels addition in a new streets of rage game LOL,or maybe it could boost colors by using shadow highlight or just extra processing speed too acces the 512 colors in screen,I know if sega didnt make a 32X il bet wed see a genesis walking on ice to cool of its heatsinks,that the hardware was so far pusheed that its or on par with snes or surpassed it because i know sega+Developers had the spirit to make the genesis turn overdrive,i stil prefer the overall graphics of many color limited games of the genesis over snes man the sharpness the small pixels the 4 layer paralax technics 3D it all did it without help of any chip so Genesis is a Very Raw beast.BTW whos got the most slick model of em al yes genesis 3 how hard it may suck Lol.

kool kitty89

03-04-2009, 01:25 AM

Sorry for starting up an old thread, but I think this topic is really interesting. (and I couldn't find a similar recent one)

That article parallels what I have been thinking about for a while. (I love looking back and thinking about such "What if" possibilities)

A couple notes though: The Saga statement on the SNES chips quoted in this article is incorrect. Donkey Kong Country didn't use the SA-1 chip, or any enhancement chip at all, it was a standard cartridge. (albeit featuring prerendered 3D sprites and backgrounds)

Similarly, while PilotWings did use the DSP-1 chip to enhance Mode 7, F-Zero did not, it was a stock cartridge using native hardware.

Now, as to Sega's options, I agree that the SVP chip is a good option and a "lock on" or jumper cart containing it is probably the best way to go about it. Ideally they should have released this jumper cart pack-in with the first SVP title: Virtua Racing; then later sold it seperately as well. (much like Star FOx 64 with the Rumble Pak)

Now, the SVP chip was good for some added processing power for things not suited for the Sega CD (as well as for games that arn't large enought to need a CD). Possibly the best of the 32X games like Knuckles Chaotix, Star Wars Arcade, and Doom. (the last of which may have turned out better overall on SVP, assuming it wasn't rushed)

However, alongside the SVP cart, the Sega CD still has a lot of untapped potential. The added scaling hardware should have allowed a good port of Wolfenstein 3D. (which should have happened earlier, like '93 but was ignored for whatever reason)
The Scaling ability would also have been gret for Sprite Based scrolling shooter games like Galaxy Force, which struggled on the stock genesis. (possibly giving a game to rival Star Fox, but with with sprites rather than primitive polygons)

A decent port of Wolf 3D may have even been possible on the stock genesis, going by the feats of Zero Tolerance and Battle Frenzy. (not to mention a few others) Particuly with some good programming tricks. (and couldn't some games overclock the CPU to 13.4 MHz for added power?)

Scooter

03-04-2009, 11:08 PM

This guy claims to have begun to be able to emulate the SVC chip.

http://notaz.gp2x.de/svp.php

kool kitty89

03-04-2009, 11:51 PM

TmEE

03-05-2009, 06:10 AM

If Sega was going to use any chip for Genesis games, I don't think the SVP would have been the best one to use. As already mentioned, it was very expensive and seemed to use a very low (even for the Genesis) color palette. Plus it was made by Samsung. Freakin' Samsung! I'm surprised it even works. If they wanted to put a chip in cartridges, it should be a chip that allowed more color and maybe two or 3 more PCM sound channels (or even PWM). That's it. Cheap to produce, no need for a giant, ugly cartridge like VR, and no need to charge $99 for each game. Games back then already cost an average of $60 or more brand new. They could have kept that price and had games with a bit more color and better digitized sound. Imagine how good Street Fighter would have looked/sounded, especialy with 40 power-packed megs! Maybe 41 just for good measure.

How good things look depends on the game itself if it uses SVP... SVP only draws you 15 color polygon stuff into a small buffer in the chip which uses same memory layout as MD VDP uses so you DMA the data from that buffer to VRAM so it could be seen.... to get more colors, you need to be creative... you have 15color per tile and sprite limit and you cannot go over it that easily.

PWM sucks, 8 resistor DACs sound better than PWM ever could.

And Steve Snake said at som point that MD could have done VR alone, withuot SVP, and same if not greater speed.

Fun fact: the PCB in SVP cart would fit into regular cart if you cut off few mm of unused PCM on top and work around the screw holes.

kool kitty89

03-05-2009, 05:20 PM

Would it have helped if the SVP cart (lets assume the "ideal" SVP adaptor/lock-on cart) also carried some additional RAM to expand the video RAM?

Did the SNES have similar limitiations in their polygonal Super FX games? Granted the SNES's much larger color palette and other advantages in this area should help things somewhat. (although I think the SNES also only had 64 KB of VRAM)

Also, do the background layers (clouds, sky, etc) have seperate color limitations? (at least in Star Fox some of the back grounds seem to be more colorful. (though it's harder to compare in Virtua Racing as there's only the blue and white Sky)

And Steve Snake said at som point that MD could have done VR alone, withuot SVP, and same if not greater speed.

How would they have been able to do that? Using the Z80 as a coprocessor as EA did for LHX and F-22?
Or would overclocking have worked? Could the 13.4 MHz speed be activated through software? (As Nick Gibson seems to imply in his FPS article)

And a note on the sound: as the article states, the SVP chip DID provide two additional sound channels. (granted they were PWM channels)

segagamer

03-05-2009, 08:42 PM

Oh, I was going to mention something on that too. The current version of Fusion (the Sega MS/Genes/32x/Saturn emulator) emulates the SVP chip fine. I've played Virtua racing on it and it works great!
(see emulator-zone.com for Fusion)

Really??? Can you provide a screen capture? BTW, Fusion does not emulate Saturn, but it does emulate Game Gear.

Chilly Willy

03-05-2009, 08:51 PM

Would it have helped if the SVP cart (lest assume the "ideal" SVP adaptor/lock-on cart) also carried some additional RAM to expand the video RAM?

You can't expand the video ram as that's only accessible to the VDP. You can provide additional ram to store patterns and such that you then DMA into VRAM... which you can already do with the ram on the SVP cart (it has an additional 128 KB if I remember correctly).

Or would overclocking have worked? Could the 13.4 MHz speed be activated through software? (As Nick Gibson seems to imply in his FPS article)

I don't think he understood about overclocking when he wrote that. He probably read one article on someone overclocking their Genesis and completely overlooked (or forgot about) all the work it took to make the Genesis work at the higher clock rate. Anything more than a couple megahertz requires desoldering the 68000 and replacing it with a faster version. Other parts on the motherboard may need additional cooling with the higher clock rate. Finally, many things simply won't work with the higher clock rate. There's no simple way to overclock the Genesis and have hardly anything work.

And a note on the sound: as the article states, the SVP chip DID provide two additional sound channels. (granted they were PWM channels)

That's still not confirmed.

Anywho, the main limitation on the SVP was that you were left with the normal Genesis graphics. The limitations on resolution and colors and the rate you could update the display were the main reason the 32X had its own VDP and framebuffers. Making the SVP into something that would have been useful leads you directly into the 32X. Instead of a Samsung DSP, you have two SH2s. Instead of 128 KB of local ram, you have 256 KB of local ram. Instead of relying on the Genesis graphics, you have a new VDP and 256 KB of framebuffer ram. And you do indeed have the PWM audio out (which the SVP may or may not have).

kool kitty89

03-05-2009, 11:43 PM

Really??? Can you provide a screen capture? BTW, Fusion does not emulate Saturn, but it does emulate Game Gear.

Yeah, it works fine. I downloaded Fusion 3.6 off emulator-zone.com and got the Virtua Racing ROM from freeroms.com (also available on coolrom.com)

Chilly Willy, isn't overclocking the Model 1 as simple as soldiering a pin from the CPU onto pin 15B of the cart slot? (along with a switch to allow boot up in 7.6/7.4 MHz mode, to avoid glitches) I've read it's a bit tougher on the Model II (only 10 or 12 MHz easily, and less stabil than the M1's 13.4 MHz) Either way, this is all modding in hardware, to do this through the cartridge with software switching it would be something else. (what is the cart slot's 13.4 MHz signal on pin 15B used for anyway)

The 32x is obviously far more powerful (and adds more colors and better sound hardware), but of course has it's own issues, being expensive, difficult to program for (though the Saturn was too) and having little support. (and having the Saturn being released in Japan)

The SVP chip could have provided a simpler cheaper alternative (particularly packaged in a Sonic & Knuckles like cart). It should be cheaper than the Sega CD (though that certainly had a lot of untapped potential for some great games) and suited for games that easily fit on a cartridge. Like the Super FX chip it was designed for drawing polygons, but it should have (like the FX chip) have allowed better scaling capabilities and other enhanced 2D effects. (of course the Sega CD could do much of this as well)

Knuckles Chaotics should have been possible (with fewer colors) and probably a fair number of others. (Star Wars arcade may have worked OK)
Doom may be a bit iffy, having only 15 (or is it 16) colors available for poligonal envirnoments would limit it (and it would likely end up without textured floors or ceilings) but the sprites should have been decently colorful (though as usual a bit high on contrast) and the framerate should be a bit smoother than with the SNES. (the sound should be decent as well, without the rush of the 32x version, the music should have been fine, like being synthesized on a Soundblaster 16)

Wolfenstein (and similar such games) should have been easy, as would it be on the CD. Even the stock Genesis may have been capable, though maybe a bit choppy. (given Zero Tolerance, Battle Frenzy/Bloodshot, "Duke Nukem 3D" and the level in Toy Story)

Overall though choosing the SVP chip may not have been the best choice anyway, why not just use a 23 MHz SH-2 processor instead. (by its self) That should offer more power, but given the surprising cost of the SVP chip, it would seem similar in that respect.

Otherwise just sticking with the stock Gennisis and CD may have worked (either way they should have done more with the CD), but for the large numbers of customers lacking a Sega CD this coprocessor cart (particularly if packaged with the first release game) should have offered both an alternative and had the added ability of polygon rendering. (the Sega CD was quite capible at scaling and rotation)

A seperate issue would be what Sega's true 5th gen console should have been like (in terms of design, not to mention marketing esp. in the US), but I don't want to get too far into that. (I may want to start a thread on that if there isn't one already) Basicly, something simpler, less expensive, and easier to program for. (something closer along the lines of the Playstation, with a single, faster CPU, possibly one upping the PS with somthing the the 40 MHz range)

segagamer

03-06-2009, 12:51 AM

Yeah, it works fine. I downloaded Fusion 3.6 off emulator-zone.com and got the Virtua Racing ROM from freeroms.com (also available on coolrom.com)

Chilly Willy, isn't overclocking the Model 1 as simple as soldiering a pin from the CPU onto pin 15B of the cart slot? (along with a switch to allow boot up in 7.6/7.4 MHz mode, to avoid glitches) I've read it's a bit tougher on the Model II (only 10 or 12 MHz easily, and less stabil than the M1's 13.4 MHz) Either way, this is all modding in hardware, to do this through the cartridge with software switching it would be something else. (what is the cart slot's 13.4 MHz signal on pin 15B used for anyway)

The 32x is obviously far more powerful (and adds more colors and better sound hardware), but of course has it's own issues, being expensive, difficult to program for (though the Saturn was too) and having little support. (and having the Saturn being released in Japan)

The SVP chip could have provided a simpler cheaper alternative (particularly packaged in a Sonic & Knuckles like cart). It should be cheaper than the Sega CD (though that certainly had a lot of untapped potential for some great games) and suited for games that easily fit on a cartridge. Like the Super FX chip it was designed for drawing polygons, but it should have (like the FX chip) have allowed better scaling capabilities and other enhanced 2D effects. (of course the Sega CD could do much of this as well)

Knuckles Chaotics should have been possible (with fewer colors) and probably a fair number of others. (Star Wars arcade may have worked OK)
Doom may be a bit iffy, having only 15 (or is it 16) colors available for poligonal envirnoments would limit it (and it would likely end up without textured floors or ceilings) but the sprites should have been decently colorful (though as usual a bit high on contrast) and the framerate should be a bit smoother than with the SNES. (the sound should be decent as well, without the rush of the 32x version, the music should have been fine, like being synthesized on a Soundblaster 16)

Wolfenstein (and similar such games) should have been easy, as would it be on the CD. Even the stock Genesis may have been capable, though maybe a bit choppy. (given Zero Tolerance, Battle Frenzy/Bloodshot, "Duke Nukem 3D" and the level in Toy Story)

Overall though choosing the SVP chip may not have been the best choice anyway, why not just use a 23 MHz SH-2 processor instead. (by its self) That should offer more power, but given the surprising cost of the SVP chip, it would seem similar in that respect.

Otherwise just sticking with the stock Gennisis and CD may have worked (either way they should have done more with the CD), but for the large numbers of customers lacking a Sega CD this coprocessor cart (particularly if packaged with the first release game) should have offered both an alternative and had the added ability of polygon rendering. (the Sega CD was quite capible at scaling and rotation)

A seperate issue would be what Sega's true 5th gen console should have been like (in terms of design, not to mention marketing esp. in the US), but I don't want to get too far into that. (I may want to start a thread on that if there isn't one already) Basicly, something simpler, less expensive, and easier to program for. (something closer along the lines of the Playstation, with a single, faster CPU, possibly one upping the PS with somthing the the 40 MHz range)

Thanks for the info...I did not realize that a new version was recently released. BTW, 3.61 has also been released.

Chilly Willy

03-06-2009, 12:54 AM

Yeah, it works fine. I downloaded Fusion 3.6 off emulator-zone.com and got the Virtua Racing ROM from freeroms.com (also available on coolrom.com)

Yes indeed, both Fusion and PicoDrive emulate the SVP chip in VR. PicoDrive on the PSP also emulates the SVP, but it doesn't yet have dynamic recompilation, so it's not playable... WAY too slow (but it does work).

Chilly Willy, isn't overclocking the Model 1 as simple as soldiering a pin from the CPU onto pin 15B of the cart slot? (along with a switch to allow boot up in 7.6/7.4 MHz mode, to avoid glitches)

Depends on the CPU package on the mobo. If I remember correctly, the ceramic package will overclock that high, but not the plastic. In any case, it will vary by the unit.

I've read it's a bit tougher on the Model II (only 10 or 12 MHz easily, and less stabil than the M1's 13.4 MHz)

From what I've read from people who have tried, it's hard to get the model 2 to break 10 MHz.

Either way, this is all modding in hardware, to do this through the cartridge with software switching it would be something else. (what is the cart slot's 13.4 MHz signal on pin 15B used for anyway)

From recent info on a thread on SpritesMind on this pin, the frequency varies quite a bit around the average of 13.4. It was probably a debug line of some kind, or used for some kind of hardware on the debug cart SEGA devs had.

The 32x is obviously far more powerful (and adds more colors and better sound hardware), but of course has it's own issues, being expensive, difficult to program for (though the Saturn was too) and having little support. (and having the Saturn being released in Japan)

The SVP chip could have provided a simpler cheaper alternative (particularly packaged in a Sonic & Knuckles like cart). It should be cheaper than the Sega CD (though that certainly had a lot of untapped potential for some great games) and suited for games that easily fit on a cartridge. Like the Super FX chip it was designed for drawing polygons, but it should have (like the FX chip) have allowed better scaling capabilities and other enhanced 2D effects. (of course the Sega CD could do much of this as well)

Yes, the SVP by itself in a lock-on style cart like S&K would have been a fairly cheap add-on that would have boosted games quite a bit, if only because it gave you another 128 KB of ram to do stuff in. The 64 KB in a stock MD is VERY limiting. I'd have bought an SVP lock-on cart for certain. After all, I did buy the CD and 32X. The SVP would have been no big deal.

Knuckles Chaotics should have been possible (with fewer colors) and probably a fair number of others. (Star Wars arcade may have worked OK)
Doom may be a bit iffy, having only 15 (or is it 16) colors available for poligonal envirnoments would limit it (and it would likely end up without textured floors or ceilings) but the sprites should have been decently colorful (though as usual a bit high on contrast) and the framerate should be a bit smoother than with the SNES. (the sound should be decent as well, without the rush of the 32x version, the music should have been fine, like being synthesized on a Soundblaster 16)

Wolfenstein (and similar such games) should have been easy, as would it be on the CD. Even the stock Genesis may have been capable, though maybe a bit choppy. (given Zero Tolerance, Battle Frenzy/Bloodshot, "Duke Nukem 3D" and the level in Toy Story)

You'd have had to rewrite many of those games from scratch due to the limited ram. If they REALLY wanted to make it useful, they would have put 1 MB on it instead. But that would have boosted the price quite a bit at the time.

Overall though choosing the SVP chip may not have been the best choice anyway, why not just use a 23 MHz SH-2 processor instead. (by its self) That should offer more power, but given the surprising cost of the SVP chip, it would seem similar in that respect.

Yeah, just one SH2 instead of two. The decision to go with two in the 32X was probably because the Titan arcade board and the Saturn had two SH2s, so it made conversions between all of them easier.

Otherwise just sticking with the stock Gennisis and CD may have worked (either way they should have done more with the CD), but for the large numbers of customers lacking a Sega CD this coprocessor cart (particularly if packaged with the first release game) should have offered both an alternative and had the added ability of polygon rendering. (the Sega CD was quite capible at scaling and rotation)

The CD graphics array is capable of polygon rendering as well. I'm doing some experiments in that to see what kind of speed I can get. Of course, it's still 16 color rendering only.

A seperate issue would be what Sega's true 5th gen console should have been like (in terms of design, not to mention marketing esp. in the US), but I don't want to get too far into that. (I may want to start a thread on that if there isn't one already) Basicly, something simpler, less expensive, and easier to program for. (something closer along the lines of the Playstation, with a single, faster CPU, possibly one upping the PS with somthing the the 40 MHz range)

The Dreamcast was more along that line: one SH4, a PowerVR video chip, some other chip to do the audio, and that's it (as far as the programmer was concerned). A less powerful version of the DC would have been better than the Saturn for developers.

kool kitty89

03-06-2009, 02:38 AM

Good points! Interesting on the Sega CD rendering polygons, I wonder what it's capable of. (though the stock Gen could, of course be forced to do it... very slowly)

You'd have had to rewrite many of those games from scratch due to the limited ram. If they REALLY wanted to make it useful, they would have put 1 MB on it instead. But that would have boosted the price quite a bit at the time.

You mean that games like Wolfenstein and Doom would have to be rewriten due to lack of RAM? (Chaotix would be different from the Start if there wasn't a 32X)
Was the added RAM of the CD needed for the port of Wing Commander? (Did the SNES version have to have a lot of reprogramming to work with its limited RAM?)

On the SVP itsself, do you know if it had a 32 bit or 16 bit core? the article lists the bus size, but not the core. (how about the FX chip's core?)

Chilly Willy

03-06-2009, 03:47 AM

Good points! Interesting on the Sega CD rendering polygons, I wonder what it's capable of. (though the stock Gen could, of course be forced to do it... very slowly)

You mean that games like Wolfenstein and Doom would have to be rewriten due to lack of RAM? (Chaotix would be different from the Start if there wasn't a 32X)
Was the added RAM of the CD needed for the port of Wing Commander? (Did the SNES version have to have a lot of reprogramming to work with its limited RAM?)

No idea about Wing Commander, but Doom definitely needs work to fit into less than 256 KB of RAM. You have to use the ROM to make up for the fact that DOOM would normally not work with less than 2 MB of ram. You decompress and store in ROM anything that would normally be decompressed into a ram buffer. This means you're taking a lot of ROM space since it can't be compressed. That's why DOOM 32X doesn't have everything. If they could have made a 32 MB ROM, Doom 32X probably would have been identical to the PC version. Squeezing it into 4 MB meant they had to simplify levels, and toss out half the game.

On the SVP itsself, do you know if it had a 32 bit or 16 bit core? the article lists the bus size, but not the core. (how about the FX chip's core?)

If you look at the docs, the SVP is a 16 bit DSP, but can do some 32 bit operations (mostly multiply and multiply-accumulate). I'm not familiar with the SNES or its chips, nor most of its games. Never cared much about the SNES.

TmEE

03-06-2009, 08:01 AM

You CANNOT use the 13.4MHz clock for CPU, at least not activate it in software. you will need to do some more modding for it to work (and all that modding happens in MD not cart), and MD2s will not like anything over 10MHz.

SVP does NOT add more sound channels, if it does, the audio pins on cartslot sure aren't connected.

kool kitty89

03-06-2009, 07:30 PM

No idea about Wing Commander, but Doom definitely needs work to fit into less than 256 KB of RAM. You have to use the ROM to make up for the fact that DOOM would normally not work with less than 2 MB of ram. You decompress and store in ROM anything that would normally be decompressed into a ram buffer. This means you're taking a lot of ROM space since it can't be compressed. That's why DOOM 32X doesn't have everything. If they could have made a 32 MB ROM, Doom 32X probably would have been identical to the PC version. Squeezing it into 4 MB meant they had to simplify levels, and toss out half the game.

How could they manage all those levels on the Supper Nintendo then? It had similar DRAM limitations to the Genesis. (64kB main and 64kB video)

Would Wolfenstein 3D be possible without RAM expansion or extensive modification?

If you look at the docs, the SVP is a 16 bit DSP, but can do some 32 bit operations (mostly multiply and multiply-accumulate). I'm not familiar with the SNES or its chips, nor most of its games. Never cared much about the SNES.

Thanks, but which docs are you referring to, does the article link to them?

So, one of the 32X's 23 MHz SH-2 processors would be a lot more powerful than the SVP, would an SH-1 be a better value? (would the cost be similar, or only moderately greater than the SVP?)

You CANNOT use the 13.4MHz clock for CPU, at least not activate it in software. you will need to do some more modding for it to work (and all that modding happens in MD not cart), and MD2s will not like anything over 10MHz.

SVP does NOT add more sound channels, if it does, the audio pins on cartslot sure aren't connected.

Got it, the author of the FPS article misinterpreted what he'd read about overclocking.

Are you positive about the sound expansion? Chilly Willy said it's unsubstantiated, but this article does mention the capability for 2 added PWM channels. If your observations are based on Virtua Racing, it's possible that VR simply didn't take advantage of this feature.

TmEE

03-06-2009, 07:34 PM

I have the VR cart and 2 pins that are supposed to carry sound are unconnected. No other pins on MD cartslot can carry analog sound

Chilly Willy

03-06-2009, 09:30 PM

Thanks, but which docs are you referring to, does the article link to them?

http://notaz.gp2x.de/svp.php

So, one of the 32X's 23 MHz SH-2 processors would be a lot more powerful than the SVP, would an SH-1 be a better value? (would the cost be similar, or only moderately greater than the SVP?)

I have no idea what Samsung charged for the 1601 (SVP). It was probably dirt cheap, which is why SEGA used it instead of an SH1 or SH2. At the time SEGA was using SH2s, there wouldn't have been a reason to use an SH1 instead.

kool kitty89

03-06-2009, 10:33 PM

[url]
I have no idea what Samsung charged for the 1601 (SVP). It was probably dirt cheap, which is why SEGA used it instead of an SH1 or SH2. At the time SEGA was using SH2s, there wouldn't have been a reason to use an SH1 instead.

Then what made Virtua Racing so expensive?

TmEE, you never explained my question about this:

And Steve Snake said at som point that MD could have done VR alone, withuot SVP, and same if not greater speed.

Can you point me to the article or discussion that mentions this?

Chilly Willy

03-06-2009, 10:41 PM

I have no idea what Samsung charged for the 1601 (SVP). It was probably dirt cheap, which is why SEGA used it instead of an SH1 or SH2.Then what made Virtua Racing so expensive?

Low volume. The memory and SVP were probably about the same price, but most of the cost was in design and manufacturing. SEGA would have needed to sell a ton of carts to afford to sell them for barely more than cost for the increase due to the SVP and memory.

Again, this might have been better if they'd made the SVP part separate from the game. By adding it into the game, they only sold as many as there were people interested in the game, and that wasn't enough to get the volume they needed. If it had been separate with a promise of future games using it, they could have sold more, making it easier to lower the price.

kool kitty89

03-07-2009, 12:57 AM

That makes sense. Considering all the development spent on a custom chip, I wonder how the costs would compare with just going the SH-2 route. (of course, we don't have any info to compare the costs so there's only speculation)

Also, maybe you missed my other part of the response (I put it in bold inside the quote), so:
Do you have any idea how they could have managed all those levels on the Supper Nintendo port of Doom? (a 2 MB/16 Mb cart) It had similar RAM limitations to the Genesis. (with 64 kB main and 64 kB video)

And:
Would Wolfenstein 3D be possible without RAM expansion or extensive modification? (with the Sega CD it should hav been easy given that the PC version only required 640 kB) But again, they managed in on the Super NES. (on a 1 MB/8 Mb cart)

Chilly Willy

03-07-2009, 08:42 AM

Do you have any idea how they could have managed all those levels on the Supper Nintendo port of Doom? (a 2 MB/16 Mb cart) It had similar RAM limitations to the Genesis. (with 64 kB main and 64 kB video)

SNES Doom used the Super FX 2 chip. That is a 21 MHz custom RISC processor. It also had extra RAM to go with it. So the custom RISC CPU was running a REALLY cut down version of Doom in its own RAM, and periodically DMAing the video to the SNES VRAM. The SNES itself did little more than play the music and sound effects. So in a way, it's nearly the same as the 32X version. They squeezed 22 levels into the space they did by getting rid of all ceilings and floors, simplifying the wall textures, and getting rid of all monster sprites except for forward facing ones.

Would Wolfenstein 3D be possible without RAM expansion or extensive modification? (with the Sega CD it should hav been easy given that the PC version only required 640 kB) But again, they managed in on the Super NES. (on a 1 MB/8 Mb cart)

The PC version uses a LOT more than 640 KB... it's closer to 2 MB.

The SNES version of Wolf3D is not based on the PC version, but a special assembly language version done specifically for the SNES and the Apple IIGS as they both had the same CPU. It didn't work at all the same way as the PC version, using a completely difference game engine (since the SNES/Apple IIGS were incapable of running the original game engine).

Anyway, Wolf3D can probably be done on the SEGA CD, but the graphics will suffer since W3D is meant to be run in 256 color mode.

TmEE

03-07-2009, 02:09 PM

Can you point me to the article or discussion that mentions this?

It is SOMEWHERE in Eidolon's Inn IIRC

kool kitty89

03-07-2009, 04:10 PM

SNES Doom used the Super FX 2 chip. That is a 21 MHz custom RISC processor. It also had extra RAM to go with it. So the custom RISC CPU was running a REALLY cut down version of Doom in its own RAM, and periodically DMAing the video to the SNES VRAM. The SNES itself did little more than play the music and sound effects. So in a way, it's nearly the same as the 32X version. They squeezed 22 levels into the space they did by getting rid of all ceilings and floors, simplifying the wall textures, and getting rid of all monster sprites except for forward facing ones.

I already knew about the Super FX 2 used for doom. (the custom Argonaut Risc Core), obviously the Genesis would need the SVP chip (or similar) to manage it. Note that the 32x version only has foreward facing sprites as well.
Also, I'd though the lack of textures on floor or ceiling was due to processing limitations (the frame rate was pretty slow) rather than memory.
Interesting to note that some parts of the environment that were missing from even the Jaguar version, like the pillars in fron of the armor at the start of level 1, are present in the SNES version, and there are some added wall textures that the 32x lacks. (of course other parts of the environments are missing, like the grating/fence walls in the last room of E1M1)

The PC version uses a LOT more than 640 KB... it's closer to 2 MB.

The SNES version of Wolf3D is not based on the PC version, but a special assembly language version done specifically for the SNES and the Apple IIGS as they both had the same CPU. It didn't work at all the same way as the PC version, using a completely difference game engine (since the SNES/Apple IIGS were incapable of running the original game engine).

Anyway, Wolf3D can probably be done on the SEGA CD, but the graphics will suffer since W3D is meant to be run in 256 color mode.

According to wikipedia's page the system requirement was 640 kB, though this site: http://www.3drealms.com/wolf3d/ lists the minimum requitement of system memory as 528 kB, though 2 MB was recomended.

It is SOMEWHERE in Eidolon's Inn IIRC

Do you mean this article?
http://www.eidolons-inn.net/tiki-view_forum_thread.php?comments_parentId=4633&topics_offset=93&topics_sort_mode=lastPost_desc&forumId=10

As this statement was scrutinized and rebuted by several other members. (and was not elaborated on)

Chilly Willy

03-07-2009, 06:28 PM

I already knew about the Super FX 2 used for doom. (the custom Argonaut Risc Core), obviously the Genesis would need the SVP chip (or similar) to manage it. Note that the 32x version only has foreward facing sprites as well.
Also, I'd though the lack of textures on floor or ceiling was due to processing limitations (the frame rate was pretty slow) rather than memory.
Interesting to note that some parts of the environment that were missing from even the Jaguar version, like the pillars in fron of the armor at the start of level 1, are present in the SNES version, and there are some added wall textures that the 32x lacks. (of course other parts of the environments are missing, like the grating/fence walls in the last room of E1M1)

All the consoles skimped somewhere to save space. The Jaguar skimped the least, while consoles like the SNES skimped the most.

According to wikipedia's page the system requirement was 640 kB, though this site: http://www.3drealms.com/wolf3d/ lists the minimum requitement of system memory as 528 kB, though 2 MB was recomended.

Hmm... I seem to remember now a 286 assembly language only version. Maybe that one would work in 512 KB. Certainly not the regular PC version.

mick_aka

03-07-2009, 08:39 PM

Chilly Willy

03-07-2009, 09:51 PM

http://i209.photobucket.com/albums/bb87/segasaturnuk/1021807217-00.jpg

Standard PC (shareware) version runs ok on my IBM PC AT with 640k, although that is with no sound as I don't have a sound card installed in it.

When I say "PC version", I mean the version based on the code that was eventually released that 99% of ports are based on.

kool kitty89

03-08-2009, 05:59 PM

Chilly Willy

03-08-2009, 06:22 PM

I don't want to take this too off topic, but Wolf 3D (being a PC game) did all the "3D" scaling (raycasting) effects through software, utilizing the CPU. To take full advantage of the Sega CD (or SNES) it would need to be reprogrammed to take advantage of the hardware scaling capabilities, correct? (though the CD's CPU may have been fast enought alone, and there was a fair amount of RAM)

If you rewrote the game in assembly, it would be probably very similar to using a 286. Just remember that you didn't run Wolf3D full screen on a 286 and expect it to be playable - that took a 386 or better. Using the CD gate array, you might be able to pull that off. The main problem would be switching to 16 color graphics. Think of it like having EGA rather than VGA graphics. The other issue would be the speed of the CD. A PC would have a pretty fast harddrive to pull data from. The SEGA CD used a 1X CDROM. When you needed to reload data off the drive (which you would with only 512 KB-ish), you'd be waiting full seconds on the CD. We'd consider the old drives the 286 used slow by today's standards, but compared to a 1X CDROM, they were lightning fast. :D

But yes, I do think Wolf3D is doable using just the SEGA CD. It would be better with the 32X, but you'd still have an issue with delays due to the slow CDROM. Even the 32X can't make the CDROM any faster.

Of course, some games (Battle Frenzy, Zero Tolerance, etc) were done on the stock Genesis throgh software (though the limitations showed). It's too bad no games took advantage of the CD's scaling effects like that. (could have made for some pretty good FPS's)

Anyway, would anyone care to speculate what an adaptor cart using an SH-2 (32X processor) would have cost? (I beleive the stand alone SVP cart was to be arround $50)

And exactly how expensive would ram expansion be? (if they encorporated something like 1 MB on the cart as well)

Hard to say. Like I said before, prices are often set by the volume, not the parts. You could make a 32X-ish kind of cart NOW very cheap. Back then? Look at the price of the 32X and then scale it back a little.

kool kitty89

03-10-2009, 05:26 AM

If you rewrote the game in assembly, it would be probably very similar to using a 286. Just remember that you didn't run Wolf3D full screen on a 286 and expect it to be playable - that took a 386 or better. Using the CD gate array, you might be able to pull that off. The main problem would be switching to 16 color graphics. Think of it like having EGA rather than VGA graphics. The other issue would be the speed of the CD. A PC would have a pretty fast harddrive to pull data from. The SEGA CD used a 1X CDROM. When you needed to reload data off the drive (which you would with only 512 KB-ish), you'd be waiting full seconds on the CD. We'd consider the old drives the 286 used slow by today's standards, but compared to a 1X CDROM, they were lightning fast. :D

But yes, I do think Wolf3D is doable using just the SEGA CD. It would be better with the 32X, but you'd still have an issue with delays due to the slow CDROM. Even the 32X can't make the CDROM any faster.

Would the use of assembly language be for compatability with the 68K architecture, or to take advantage of the scaling hardware?

Why would a 32X version need to be on CD? Surely a ROM cartridge would be sufficient. (being in the 2-3 MB size)

Do you think games like Wolf3D could have been done in assembly with the SVP alone without added RAM?

Also, I know the background would have to be limited 16-colors, but wouldn't sprites have the other 3 16-color palettes available to use?

Hard to say. Like I said before, prices are often set by the volume, not the parts. You could make a 32X-ish kind of cart NOW very cheap. Back then? Look at the price of the 32X and then scale it back a little.

Yep, and the lower cost of the SVP chip would have overcome the development costs for such a custom chip with enough volume in sales. But it's a question of how much volume it would take to make it worth using over somthing like an SH-2. (added RAM would be the same price regardless)

As an in-cart chip (like the FX) it'd be a no brainer that the SVP would be cheaper (assuming you released more than one game using it, with the single release a lock-on cart would obviously be pointless). However, in a lock-on set up the circumstances are a bit different (the volume would be independent of the number of games produced using it) and the added RAM becomes feasible. (wich would be prohibitably expensive on an in-game cart if used in any significant amount)

Chilly Willy

03-10-2009, 07:00 AM

Would the use of assembly language be for compatability with the 68K architecture, or to take advantage of the scaling hardware?

Neither. It would be to maximize speed while minimizing the space required by the code.

Why would a 32X version need to be on CD? Surely a ROM cartridge would be sufficient. (being in the 2-3 MB size)

Since I released the cart version, people have been bugging me for a CD version as well. There are a few reasons. First, you wouldn't need a flash cart to play it on real hardware. Second, you could support the commercial versions with the same executable. I obviously can't release versions of Wolf32X using the full files, just the shareware ones.

Do you think games like Wolf3D could have been done in assembly with the SVP alone without added RAM?

With the extra ram the SVP had, probably. With just the 64 KB in the Genesis itself? You'd have to chop it up too much. For example, just tracking the "objects" used by Wolf3D (items, enemies, etc) requires a lot of ram. You could do a raycasting type game, but it wouldn't really be Wolf3D. So if you meant a game in the same genre, yes, the SVP would handle that just fine. With some judicious use of assembly, it could probably even handle Doom-genre games. But Wolf3D or Doom themselves? You could make something that imitated it, but wasn't really Wolf3D or Doom. It depends on how picky you are about what you call Wolf3D or Doom. :D

Also, I know the background would have to be limited 16-colors, but wouldn't sprites have the other 3 16-color palettes available to use?

Yes, that's one of the things that could be done to help with the graphics. Use the palettes for objects separately from the background.

Yep, and the lower cost of the SVP chip would have overcome the development costs for such a custom chip with enough volume in sales. But it's a question of how much volume it would take to make it worth using over somthing like an SH-2. (added RAM would be the same price regardless)

As an in-cart chip (like the FX) it'd be a no brainer that the SVP would be cheaper (assuming you released more than one game using it, with the single release a lock-on cart would obviously be pointless). However, in a lock-on set up the circumstances are a bit different (the volume would be independent of the number of games produced using it) and the added RAM becomes feasible. (wich would be prohibitably expensive on an in-game cart if used in any significant amount)

What I'd love to see is a new cart that had a FPGA and some ram on it. You could actually program the FPGA to act as the SVP. That would allow the creation of SVP games other than Virtua Racing.

TmEE

03-10-2009, 07:26 AM

The FPGA cart would be fun thing to mess with, and with that you have freedom to enhance stuff, perhaps a nice patterntable and tile generator that gives you nicely worked out 31 color data with minimal VDP bandwith requirement :P

kool kitty89

03-10-2009, 05:08 PM

With the extra ram the SVP had, probably. With just the 64 KB in the Genesis itself? You'd have to chop it up too much. For example, just tracking the "objects" used by Wolf3D (items, enemies, etc) requires a lot of ram. You could do a raycasting type game, but it wouldn't really be Wolf3D. So if you meant a game in the same genre, yes, the SVP would handle that just fine. With some judicious use of assembly, it could probably even handle Doom-genre games. But Wolf3D or Doom themselves? You could make something that imitated it, but wasn't really Wolf3D or Doom. It depends on how picky you are about what you call Wolf3D or Doom. :D

When I said without added RAM, I meant excluding the added 1-2 MB on cart possibility. However, I'd though the only added memory was the 2 kB or I-RAM (that's all Ken Horowitz's article mentioned, and for some reason listed it twice in the Super FX comparison table: under both RAM, and Memory -Cache-).
Reading through that doccument on the SVP you linked to earlier though, I now see that the Virtua Racing cart also carried 128 kB of DRAM. (incedentally the same amount carried in Super FX carts, -1 Mb according to Horowitz's article, albeit with only 1/4 the Cache RAM available)