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Thread: sega saturn theoretical backwards compatibility

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    Road Rasher chrisbid's Avatar
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    Default sega saturn theoretical backwards compatibility

    i am not the tech spec geek that a lot of other posters are on this board, so i have a question to pique their brains

    the saturn used a 68k processor to produce sound.

    so the questions are

    was this designed with the idea the saturn would be backwards compatible with sega genesis games... the same way the genesis z80 sound chip was used to play master system games?

    i would venture to guess the main saturn processors could not emulate a sega genesis like a strong pc could. in the mid 90s, sega genesis emulation on the pc, while possible, was still pretty clunky. so on releases like sonic jam and phantasy star collection, is the saturn using emulation via the 68k chip? would that even be called emulation?

    following this logic, would it be possible to make a device similar to the genesis power base convertor for the saturn? sonic jam and psc had their minor issues, but it would be kindof cool to see how feasible the original backwards compatible design wouldve worked in the real world had sega not nixed it. maybe there wouldve been too many incompatible games or software issues?

    help me out, sega-16ers!

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    Bite my shiny, metal ***! Hero of Algol retrospiel's Avatar
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    Quote Originally Posted by chrisbid View Post
    was this designed with the idea the saturn would be backwards compatible with sega genesis games... the same way the genesis z80 sound chip was used to play master system games?
    Yes, and no. The 68k most likely hints at the Saturn's early roots of being a MD compatible machine ("Giga Drive"?) but Saturn as we know it was not meant to play MD games.

    They did not want to kill the Genesis too soon so both SOJ and SOA came up with different concepts on how to proceed from here on. SOJ came up with Project Mars, an affordable compatible MD with more colors and a 3D co-processor, and SOA came up with what we now know as 32X, an add-on meant to allow Genesis owners to upgrade the machine themselves.
    Mars/32x are why they skipped MD compatibility in Saturn.

    Anyway, the MD's most powerful parts aside of the 68k are the VDP and the YM2612. A Saturn Power Base Converter equivalent would have to rely on software emulation of the VDP but also provide the entire audio hardware of the MD, consisting of the YM2612, the Z80 and the PSG.

    Not saying that it'd not have been possible but it probably wouldn't have been cheap and by late 1995 when Saturn was released in the US and EU, the 32x was still kept on life support in the EU and US, and by 1996 the MD's market had already collapsed anyway.
    Last edited by retrospiel; 04-24-2010 at 01:18 PM.
    The Mega Drive was far inferior to the NES in terms of diffusion rate and sales in the Japanese market, though there were ardent Sega users. But in the US and Europe, we knew Sega could challenge Nintendo. We aimed at dominating those markets, hiring experienced staff for our overseas department in Japan, and revitalising Sega of America and the ailing Virgin group in Europe.

    Then we set about developing killer games.

    - Hayao Nakayama, Mega Drive Collected Works (p. 17)

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    Mastering your Systems Shining Hero TmEE's Avatar
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    The 68K used in the Saturn is not 100% software compatible with vanilla 68K either, though IF they wanted MD compatibility, they would have used normal 68K, aswell as a Z80 somewhere and a YM2612 and MD VDP....... current Saturn and MD are quite night and day.

    Sonic Jam is all ports, no emulation. Music is streamed ADPCM, SFX are off the chip, and done badly....
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    Does the 68EC000 have similar modifications to the instruction set as the 68010 (and 020, etc), or does it have to do with the 68EC020's?

    Otherwise, you're of course missing all the custom silicon necessary for the MD...

    Using a 68EC000 for an audio controller was rather common and given Sega's heavy use of 68k based arcade boards (and general commonality of the chip in general), it really doesn't say much for the Saturn whatsoever.
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    Quote Originally Posted by evilevoix View Post
    Dude it’s the bios that marries the 16 bit and the 8 bit that makes it 24 bit. If SNK released their double speed bios revision SNK would have had the world’s first 48 bit machine, IDK how you keep ignoring this.
    Quote Originally Posted by evilevoix View Post
    the PCE, that system has no extra silicone for music, how many resources are used to make music and it has less sprites than the MD on screen at once but a larger sprite area?

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    ding-doaw Raging in the Streets tomaitheous's Avatar
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    I think too much people put emphasis on the 68k aspect. Really, it's just a processor. It was in a lot of hardware. It was already familiar to Sega and its development team, etc.

    following this logic, would it be possible to make a device similar to the genesis power base convertor for the saturn?
    The Power Base converter... is a glorified cart connector converter. That would imply that the Saturn already had backwards compatibility like the Genesis, but omitted the right cart connector to run them. PBC is the wrong type of analogy. I think Super Gameboy would be a better analogy. Sure, they could have done something like a SGB I guess. But it would basically be a Genesis in a shell/cart/whatever. Not a PBC.

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    I DON'T LIKE POKEMON Hero of Algol j_factor's Avatar
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    SMS: Z80 CPU
    Genesis: 68k CPU, Z80 sound controller
    Saturn: SH-2 CPUs, 68k sound controller

    It does almost suggest a pattern. What I simply can't fathom is why they didn't use dual SH-2's to control the sound in the Dreamcast. It really boggles the mind!


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    Not that I have any idea, but I get the impression that the 68K was just a convenient and powerful-enough processor to do what they needed with the sound.

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    Quote Originally Posted by j_factor View Post
    SMS: Z80 CPU
    Genesis: 68k CPU, Z80 sound controller
    Saturn: SH-2 CPUs, 68k sound controller

    It does almost suggest a pattern. What I simply can't fathom is why they didn't use dual SH-2's to control the sound in the Dreamcast. It really boggles the mind!
    Its more like this:

    SMS: z80, PSG, VDP, IO mapper, controllers;
    MD: same z80, same zRam, same PSG, VDP with "old video" modes, SMS-compatible IO mapper, SMS-compatible controllers;
    Saturn: 68k and nothing more.

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    I DON'T LIKE POKEMON Hero of Algol j_factor's Avatar
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    You're seriously overanalyzing a rather facetious post.


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    Quote Originally Posted by Jorge Nuno View Post
    Its more like this:

    SMS: z80, PSG, VDP, IO mapper, controllers;
    MD: same z80, same zRam, same PSG, VDP with "old video" modes, SMS-compatible IO mapper, SMS-compatible controllers;
    Saturn: 68k and nothing more.
    yeah but those SMS-compatible stuff wouldn't have been necessary for Saturn would it. By the time Saturn around Master System wasn't even a thought on anyone's mind, so the Saturn wouldn't needed SMS support, it could have used a Z80 or least let one of the SH-2 emulate the Z80.
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    1. SMS was still supported in 1994. It held a small share of the market in most European countries, Brasil, and Korea. Support by SOJ would remain until late 1996 / early 1997 when they stopped supporting Game Gear in Japan.

    2. "SMS compatible stuff" was part of the MD's hardware. MD was MD + SMS. MD was YM2612 + VDP + 68k and PSG, Z80, IO mapper, controllers.

    3. Yes, considering all previous Sega hardware was backwards compatible, Mega Drive compatibility was likely part of the original design of Saturn (when it still was called "Giga Drive"). But in one of Saturn's redesigns it was dropped for one reason or another (migrating users to Mars/32X/Neptune would be my guess).
    Last edited by retrospiel; 04-25-2010 at 06:54 PM.
    The Mega Drive was far inferior to the NES in terms of diffusion rate and sales in the Japanese market, though there were ardent Sega users. But in the US and Europe, we knew Sega could challenge Nintendo. We aimed at dominating those markets, hiring experienced staff for our overseas department in Japan, and revitalising Sega of America and the ailing Virgin group in Europe.

    Then we set about developing killer games.

    - Hayao Nakayama, Mega Drive Collected Works (p. 17)

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    what i meant was that SMS was not a thought on people minds who were not living in 3rd world countries.

    heck even Nintendo killed NES by 1994. 8-bit was dead in 1995, and even 2D style gaming was getting phased out.
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    ^ That doesn't change anything. MD compatibility still means SMS compatibility.

    Besides, if people enjoyed rocking their SMS in 1994 it hardly makes that a valid criterium as to whether or not they're living in a third world country... If that would be the case in which country do you and me would live in due to us still playing our MDs ? 16th world ? =P
    Last edited by retrospiel; 04-25-2010 at 07:06 PM.
    The Mega Drive was far inferior to the NES in terms of diffusion rate and sales in the Japanese market, though there were ardent Sega users. But in the US and Europe, we knew Sega could challenge Nintendo. We aimed at dominating those markets, hiring experienced staff for our overseas department in Japan, and revitalising Sega of America and the ailing Virgin group in Europe.

    Then we set about developing killer games.

    - Hayao Nakayama, Mega Drive Collected Works (p. 17)

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    Quote Originally Posted by gamegenie View Post
    heck even Nintendo killed NES by 1994. 8-bit was dead in 1995, and even 2D style gaming was getting phased out.
    There were still a lot of late adopters though, I know several people who didn't even get 16-bit era systems until '94-96 (for us it was the SNES), there's always that side of the market though, hence why the NES was still selling to a small degree in budget markets into the mid 90s. (and likely SMS in Europe) Those still have little bearing on the saturn though as such customers wouldn't be moving there for quite some time and compatibility of later MDs was a bit of a non-issue as well given how unpopular the PBC-II was.


    Also, using software emulation for some portions but not other gets rather hairy (I think the PS3 had some issues with that for PS2 compatibility), but in general the Saturn shows little if any signs of the intention to include compatibility.

    Given the way it was implemented int he MD, it probably wouldn't have hurt too much to include a few more inputs on the cart connector and support the SMS hardware built into the PBC (which was roughly large enough to carry the additional hardware already). Had they used outboard pins like the SNES, it wouldn't even add to the cost of standard cart PCBs. (and if analog RGB inputs were among the added connections, it would mean no mixing cable for the 32x) getting off topic now.
    OTOH, they probably could have made other changes to make the SMS hardware more useful in the MD (connecting the Z80 int lien to the YM2612 for one, clocking the Z80 faster in MD mode for another -a large portion of Z80s used are 6 MHz versions already, so mainly a little added cost for some early models) You'd still be wasing a fair chunk of the VDP though.

    Using the MD (and MCD) hardware in an efficient fashion in a new system presets some other possibilities that have been discussed before, but this is also getting off topic. The poit still being that the final Saturn didn't take that design route.

    Quote Originally Posted by Christuserloeser View Post
    3. Yes, considering all previous Sega hardware was backwards compatible, Mega Drive compatibility was likely part of the original design of Saturn (when it still was called "Giga Drive"). But in one of Saturn's redesigns it was dropped for one reason or another (migrating users to Mars/32X/Neptune would be my guess).
    That doesn't make too much sense... the final (re-designed) Saturn was a totally parallel project to Mars and the resulting 32x, so I really don't see how that has any bearing on the Saturn's lack of compatibility. (there's nothing in the final design with really alludes to it ever intending to have been compatible with the MD or MCD)
    The "original" Saturn (or GigaDrive) might have been another story and the original Mars (and technically 32x too) was definitely a different case.
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    Quote Originally Posted by evilevoix View Post
    Dude it’s the bios that marries the 16 bit and the 8 bit that makes it 24 bit. If SNK released their double speed bios revision SNK would have had the world’s first 48 bit machine, IDK how you keep ignoring this.
    Quote Originally Posted by evilevoix View Post
    the PCE, that system has no extra silicone for music, how many resources are used to make music and it has less sprites than the MD on screen at once but a larger sprite area?

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    From what we know, Giga Drive (which eventually evolved into Saturn) is the older project. Project Mars, which evolved into 32X and Neptune, where Neptune is pretty much the same thing as Mars (MD+), was not considered part of the company's next gen strategy until 1993 / 1994.

    My theory as to how Sega of Japan approached this would be as follows:

    1990 - 1992: Giga Drive is being developed based on the MD hardware (like SMS is based on SG-1000 and Mega Drive is based on SMS). The phenomenal success of the Genesis in the US leads to a redesign/cancelation of the hardware.
    1993 - 1994: Saturn / Mars project. A minor hardware update (Mars) is meant to keep Genesis / Mega Drive fans happy, while Saturn is developed as a 2D/3D arcade board + high end home system (much like Neo Geo and Dreamcast). Its 2D capabilities surpass System 32 hardware and its 3D capabilities are superior to Model 1 in many ways.

    Mars then was canceled and reborn as 32X in "8 January 1994, the night before the opening of the 1994 Winter CES in Las Vegas, Nevada. [...] As first presented by Hideki Sato and his team of engineers, the original concept for Mars was a Genesis with an extra 32-bit processor and an expanded color palette. Joe Miller, chief technical wizard at Sega of America, was appalled at the suggestion. "That is a horrible idea," he told them. "If all you're going to do is enhance the system, you should make an add-on. If it's a new system with legitimate software, great. But if the only thing it does is double the colors ...."
    There was some grumbling about this, but in the end Sega of Japan conceeded the point. Mars was to be Sega of America's baby.
    "
    (I filtered and shortened the shit out of Sam Pettus' mental diarriah. I fucking HATE this goddam article!)


    The idea behind releasing an add-on, 32X, and not Neptune (the 32X based equivalent of SOJ's original Mars concept), either first or at least simultaneously, translates to a strategy like this:

    1. Let's not intimidate the Genesis user base at all cost! - We ensure you, dear customer, that Genesis will remain "heart of the system" until at least 199x.

    2. We will migrate our user base to 32X first! 32X will further enhance our position against Nintendo and will prevent our users to migrate to other next gen platforms such as 3DO, Jaguar and CD32.

    3. Neptune will then replace the Genesis as our flag ship as an affordable family friendly next gen machine. Genesis will still be a valid low cost platform for many years to come.

    4. Saturn will be the high end platform for people with a higher income. During its life span production will eventually be more efficient and thus cheaper. It will then slowly replace Neptune as our new hardware flag ship. This is estimated to happen in ~1997 or 1998.


    I have an official Sega of Germany press release from late 1995 (!) that says pretty much exaclty what I wrote above.
    Last edited by retrospiel; 04-26-2010 at 08:31 AM.
    The Mega Drive was far inferior to the NES in terms of diffusion rate and sales in the Japanese market, though there were ardent Sega users. But in the US and Europe, we knew Sega could challenge Nintendo. We aimed at dominating those markets, hiring experienced staff for our overseas department in Japan, and revitalising Sega of America and the ailing Virgin group in Europe.

    Then we set about developing killer games.

    - Hayao Nakayama, Mega Drive Collected Works (p. 17)

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