Comparison of 4th generation ("8/16-bit") system hardware

[Thenewguy]

I ran into a quote about the GX4000 DMA sound today, I don't really understand how sound works well enough for it to give me a ballpark of what kind of sound quality its talking about but I'm sure you guys would. -

With DMA , ASIC can update directly AY register every line (312 per frame but there are tricks to update twice) , you can have easily 15Khz samples without CPU usage so you can manage a complete game when playing sound. (RD128+ has slowdowns when playing samples but this is because of memory restrictions in main 64K)

About sound effects , in a game on CPC when using interrupts and the CPU , you can update sound 6 time per frame (50hz) , on a + , you can update sound 312 time per frame without CPU usage.

Is that anywhere near approaching the sort of sound found in the intro of Turrican II on Atari ST?

[Crazyace]

It massively improves the usage of the AY chip by removing the heavy interupt overhead. The Z80 would still have to prepare the data to put in the DMA list though, so it's not completely free.

[kool kitty89]

Hmm, so the DMA writes only to the AY chip and not to a dedicated DAC?
That's a bit weird . . . though it would still be useful and would potentially allow 3 independent sound channels (3 AY voices), but also limit you to using nonlinear 5-bit pseudo-PCM samples (like with software playback on the AY) and only on those 3 channels. The hardwired stereo configuration would also prevent the 2/3-channel additive pseudo-linear PCM hacks used on the ST.

It would also potentially reduce overhead for PSG music. (using DMA to update notes and help with envelopes rather than needing interrupts of carefully timed code)

[saturndual32]

Hate to see such a nice thread die off.
I was wondering, regarding the Neo Geos sprite zooming capabilities. How good a port of Out Run, do you guys think it would be able to handle?. It sucks that the only example we got of a similar game is Riding hero...

[Kamahl]

Hate to see such a nice thread die off.

Glad to see people still care about it !

I was wondering, regarding the Neo Geos sprite zooming capabilities. How good a port of Out Run, do you guys think it would be able to handle?. It sucks that the only example we got of a similar game is Riding hero...

It shouldn't have any problem with it. Still, there's no actual sprite zooming on the neo geo, just shrinking. Whenever you see something that seems to be scaling, it's just drawn pre-scaled, shrunk, and then drawn "less shrunken" each frame.

[saturndual32]

So, thats why when stuff is "zoomed in" on Neo games, they dont get blocky like crazy, like on other systems like SNES and even Saturn?. Pretty cool!

[Kamahl]

So, thats why when stuff is "zoomed in" on Neo games, they dont get blocky like crazy, like on other systems like SNES and even Saturn?. Pretty cool!

The Saturn and SNES can do it too, it's just that it takes a ton of space (just like it does on the Neo Geo).
Whenever it's blocky on the Neo Geo, it's a stylistic choice.

[sheath]

It's too bad it isn't simple to go back and hack old Roms like Super Thunder Blade or even Super Mario Kart and jack up the amount of ROM space the animated sprite transitions take. It shouldn't even take that much to make the pre-rendered scaling run at 15 FPS, they just couldn't do it with the tiny ROM sizes from the time.

[Kamahl]

It's too bad it isn't simple to go back and hack old Roms like Super Thunder Blade or even Super Mario Kart and jack up the amount of ROM space the animated sprite transitions take. It shouldn't even take that much to make the pre-rendered scaling run at 15 FPS, they just couldn't do it with the tiny ROM sizes from the time.

Burning Force faked scaling pretty well (it's all prerendered but looks great):

[sheath]

Yeah, I wonder what the trade off is there. Is it sprite variation, sprites on screen, or the way the backgrounds are displayed?

Bimini Run is pretty good as well, but about Mario Kart quality in the sprite scaling animations:


Galaxy Force II is about the smoothest in the sprite scaling department I have seen on the Genesis, but it falls short in other areas like sprite flicker and sprite size. The bosses and planet surface scaling sequences are the most impressive.


I seem to remember Air Diver being impressive in spots too.

[Kamahl]

Yeah, I wonder what the trade off is there. Is it sprite variation, sprites on screen, or the way the backgrounds are displayed?

I'm honestly not sure, the framerate is just amazing, not idea how they did it.

[Thenewguy]

I've been reading up on the Atari 8-bit machines recently and I was thinking that the GX4000 is kinda' similar in some ways, the fanbases are often talking about similar things (IE 4 colour mode with pallette re-loading, multiplexing sprites horizontally etc), as well as talking about how the big colour pallette can offset low resolution mode etc. It seems as though the biggest issue with both machines is also the sprites, with per line colour limits coming in second. Of course its shifted forwards though, as the GX4000s high resolution mode is like the Atari 800s low resolution mode.

Anyway, I've run into one example of DMA sound for GX4000, but its an old one unfortunately (from the actual time), still, it sounds better than what you'd get from a normal AY at least.

[Kamahl]

16, 16x16 sprites per line isn't too bad... That's 256 pixels.
I can't see how that's anywhere near as bad as only 4, single color, 8 pixel wide sprites.

The 4 color limit is way, way worse if you want to do the whole game in high res.

[Thenewguy]

I dunno, I think for most side-on games 20-25 colours could be very do-able in high resolution, which would conceivably put it a little higher than general Atari ST graphics for specific types of games in regards to colour + resolution (with smoother scrolling too)

Changing the sprite data on the other hand seems to be a time consuming pain in the ass though unfortunately, from what I've heard multiplexing is pretty much out of the question in-game unless you're leaving the same pre-defined sprite data for your 16 sprite images (and some characters will have to be built with multiple sprites + different animation, all taking up those slots).

Someone more knowledgeable than me did say that it would probably be an idea to simply make games with 8 sprites, and update the other 8 sprite registers whilst they're off-screen, swapping between the two. From what I can recall he also mentioned that dropping the frame rate helped.

Of course I have very little understanding of this stuff, so I'm just going by what I've been told (which I only half understand), and thats just one Amstrad programmer's opinion, he considered the GX4000 to be better for sprites than the SMS, but one of the other homebrew programmers I spoke to considered GX4000 sprites to be completely worthless, and worse in his estimation even than NES sprites in all but colour.

EDIT: Also, I meant "kinda similar" in the way the system's graphics are, not in overall capabilities, like the GX4000 could be the next gen equivalent or something (and yeah, I know A8 fans call the Amiga its actual next gen descendant ).

[Kamahl]

Ah yes, multiplexing is pretty much horrible, just checked.
It's not 16 sprites per line. It's 16 sprites period. That's horrible xD.
The NES can't do multiplexing without extra chips, but it has 64 sprites...