Exploring The Sega Saturn’s Wacky Architecture

Sega Saturn mainboard with main components labelled. More RAM is found on the bottom, as well. (Credit: Rodrigo Copetti)
Sega Saturn mainboard with main components labelled. More RAM is found on the bottom, as well. (Credit: Rodrigo Copetti)

In the annals of game console history, the Sega Saturn is probably the most convoluted system of all time, even giving the Playstation 3 a run for its rings. Also known as the system on which Sega beached itself before its Dreamcast swansong, it featured an incredible four CPUs, two video processors, multiple levels and types of RAM, all pushed onto game studios with virtually no software tools or plan how to use the thing. An introduction to this console’s architecture is provided by [Rodrigo Copetti], which gives a good idea of the harrowing task of developing for this system.

Launched in Japan in 1994 and North America and Europe in 1995, it featured a double-speed CD-ROM drive, Hitachi’s zippy new SH-2 CPU (times two) and some 3D processing grunt that was intended to let it compete with Sony’s Playstation. The video and sound solutions were all proprietary to Sega, with the two video processors (VDP1 & 2) handling parts of the rendering process which complicated its use for 3D tasks, along with its use of quadrilaterals instead of triangles as with the Playstation and Nintendo 64.

Although a lot of performance could be extracted from the Saturn’s idiosyncratic architecture, its high price and ultimately the competition with the Sony Playstation and the 1996 release of the Nintendo 64 would spell the end for the Saturn. Although the Dreamcast did not repeat the Saturn’s mistakes, it seems one commercial failure was enough to ruin Sega’s chances as a hardware developer.

44 thoughts on “Exploring The Sega Saturn’s Wacky Architecture

    1. The short short version is they designed the Sega Saturn to be a Super Nintendo killer back in the early 1990s. Then PlayStation was unveiled at CES and it had 3d, and then Sega said “Oh crap! We better cram 3d processing into this thing” This next part is sourced from my memories and may be incorrect: rather than redesigning from the ground up, they essentially put the 3d hardware on the 2d hardware, and to program the 3d hardware, you had to issue the commands through the 2d hardware.

      They had a deal with Hitachi to use Hitachi’s SH2 processors, regardless of what they were doing. This was one of many poor business decisions on Sega’s part, and I think was implemented by their chairman or someone high up in the org at the time. The Ultimate History of Videogames Vol 1 and 2 are the books I’ve most recently read, though you can find this detail if you comb through forums, reddit, and wiki articles. I loved the games on the Saturn but Sega’s marketing shot itself in the foot over and over. Companies like Konami bet on the wrong horse, releasing a bad US-made Contra game instead of the visual novel epic Policenauts from Hideo Kojima, you name a company I could tell you a bad call they made with Saturn. Ultimately it lost in the market place, and Sega’s board chose to announce Dreamcast too early, cutting into sales and killing the console off roughly 2 years ahead of the Dreamcast launch.

      1. Pretty much correct. Sega cobbled a few extra parts to try and beat Playstation but didn’t plan well on this, programming for it was challenging and some developers often did Playstation first then ported to Saturn without optimizing graphics so some of the games ended up looking like it’s playing from Playstation.

        The cobbled together hardware also made it hard for Sega to consolidate chips and shrink the consoles to save money so Saturn couldn’t be sold cheap without causing Sega large loss while Sony was able to make cheaper console, ending up with a PSOne that was sold dirt cheap.

        tl;dr “hold my beer” moment gone wrong

        1. “Pretty much correct” as in almost completely wrong.

          Saturn was not suppose to kill the SNES, it was designed to be the winner of the next generation, which at the time consisted of 3DO, CDI, and Jaguar.

          Sega knew of the PSX long before CES, Sony literally approached them to make the PSX after their deal with Nintendo failed. What CES did was show that Sega got bad intel, and that they needed to add more power, which became a second SH2.

          They did not put 3D on 2D hardware. 3D was just done using quads instead of triangles. It allowed them to optimize the processor to work in tandem with the 2D. The system still had polygons, but a textured polygon worked the same way as a sprite because at the end of the day, there really was no difference.

          The SH2 was not a poor decision at all, it allowed the Saturn to get beefed up with a second processor (which itself was not a bad thing.)

          Marketing wasn’t then problem , lack of it was. Most people were not aware the Saturn even existed in launch.

          Games like Policenauts and Snatcher were not system sellers here. Anime themed content was still incredibly niche at the time. Konami was correct with Contra, just forgot how go make a good Contra game.

          Dreamcast was not announced too early. Saturn was pretty much dead by the time it was announced. The problem was how it was announced, with “the Saturn is not our future” line making developers pull out sooner instead if releasing content that was planned to flop.

          1. “Most people were not aware the Saturn even existed in launch.”
            I was not into gaming and consoles on that time but I remember that leading gaming magazine (Secret Service) was betting on Sega Saturn rather than Playstation. Selling titles were were supposed to be Virtua Fighter, Sega Rally and some one or two more games. Tech specs was claimed to be superior to PS. To me it was clear on that time that Sega would win this race.
            Anyway gamers in Poland knew about Saturn as much as about Playstation. I wonder if this was specific only for my country?

          2. PPJ wasnt ‘Secret Service’ the mag with article hailing S3 Virge as _the 3D accelerator_ to get in 1996? Same timeframe as the flood of Bobmark Saturn adverts. SS at the time was willing to print whatever provided sufficient advertising budged.

      2. The story of 3D being a last-minute addition is almost certainly not true. We know there were some late changes (e.g. a developer presentation from April 1994 specifies the main memory as 1.5MB SDRAM. An updated version of the same presentation from May 1994 specifies 1MB of SDRAM and 1MB of DRAM, which is what the final hardware has. It’s probably not a coincidence that the Playstation had 2MB of main memory), but there’s no evidence the machine wasn’t intended to play 3D games from the start.

        Sega were pioneers in 3D gaming, and they absolutely knew which way the industry was heading (Ken Kutaragi himself claimed it was only after Sega released Virtua Racing and Virtua Fighter in the arcades that third-party developers became interested in the Playstation). It makes no sense for them to design a 2D-only console.

        As for their dealings with Hitachi, I don’t think it was such a bad decision, regardless of any backroom dealings. The SH-2 architecture was an improved version of the SH-1 designed specifically based on input from Sega’s engineers, much like the SH-4 used in the Dreamcast. Hitachi also manufactured many of the Saturn’s custom ICs, and supplied e.g. the memory chips. It’s unlikely they’d receive this amount of support if they’d used commercially available devices (the rest of the custom ICs were manufactured by Yamaha, who also designed the console’s audio hardware.)

        1. The Sega Saturn architect stated that the toxic culture at Sega of Japan prevented any team from sharing information. So while Team AM was at the top, none of it’s work ever made it into the Saturn. The additional SH2 was a last minute addition and using both SH2 at the same time required a hack that wasn’t discovered until a year after the Japan launch.

    2. In the 90s the development of arcade boards secretly drove console development. For Nintendo this usually meant the older boards, as they wanted obsolete but usable technology to make consoles. Even the PS1 is dated by its contemporary era, 1994 release but 1997 saw US sales grow so these games were behind on the graphics. Sega however put a beast out, based on their newer arcade boards. This increased cost, made game development difficult, these caveats leading consumers to the SNES/PS1 and eventually the N64 and the Saturn sinking to a footnote in history without many emulation options

      1. Games – or lack thereof – killed the system. Sega gave game devs little warning when it dropped, retailers even less and never got decent games (and kept pushing other crap hardware, when they could have used all that wasted money making the Saturn have a better position). Games always win a console war. Just ask the Game Boy – which had numerous competitors with better tech – why it beat all competition.

          1. The Wii most definitely counts. Wii Sports was the game. Yes it’s a simple game with no complex strategy. But simple works for the right audience.

            Tetris is relatively simple, but it’s easy to pick up and put down. For a travel game console that you play during your commute it was perfect.

            People bought the Wii to play Wii Sports. Granny and Gramps wanted to bowl in their padded carpeted living room where they weren’t going to break a hip. There’s a reason there are still Wii consoles in retirement homes everywhere.

            A gimmick doesn’t consistently sell 10m units/yr 4 years after release. People bought it to bowl. Yes, that’s a simple reason. Yes, it was a simple game compared to most (all?) other games. But it worked, just as the Gameboy + Tetris did, for people who had never bought a video game console before.

          1. Yes but they messed up those they did release too. Panzer Dragoon Saga with s criminally low run and Shining Force 3 with just one part and a hacked together fake ending.

            If you check the CD for SF3’s Premium Disc the developers talk about the growing tension between SEGA and Camelot and about them just finishing the game off and moving on. A few years after this they became a Nintendo mainstay with Mario Tennis, Mario Golf and Golden Sun (which is more of a classic Shining game than most of the dross Sega has churned out under that title since). As far as I know Camelot refused to work with them again, for reasons I’m not sure about but probably related to them cutting their knees for their magnum opus with the Dreamcast announcement. And they were a 2nd party developer! Imagine how they treated 3rd parties.

            Years ago I remember a webpage that had the account of all this. I remember a report that towards the end of his time at Sega Tom Kalinske just stared out the windows knowing the Sega of Japan and their toxic political culture (what Yuji Naka had escaped from to build Sonic 2). They got lucky with the Megadrive but never managed to expand into a coherent large scale business after their moment of success – indeed it’s something I see at many scale-ups today.

      2. As far as I understand, Sega of America wanted to keep Genesis (Mega Drive) alive during the 90s, but Sega of Japan didn’t care.

        Sega of Japan didn’t like the MD very much, because sales in its home country of Japan weren’t doing well – in contrast to Europe, America and other places around the globe were the Mega Drive had many fans.

        In retrospect this is very sad, because the Genesis had a relationship with the Sega System 16 arcade board (and the Master System).

        That’s also why some modders try to run the Genesis’ m68k at 10 MHz, that was the clock speed of the arcade system’s CPU. Some games originally being ported over from System 16 were happy about that increase in speed. ;)


        1. Yes, Sega were weird that the Master System was big in Europe/Brazil, the Megadrive in US/Europe and the Saturn in Japan. It just shows the corporate chaos that they didn’t promote and produce games equally across markets.

      3. This is, frankly, an insane and deluded take.

        The Saturn has absolutely nothing in common with the arcade titles that Sega were making at the time. The “newer arcade boards” that you’re referring to would have been the Model 2 platform, which sported a single Intel i960 as its main CPU, and used a wide variety of daughterboards for graphics, ranging from the same mask-programmed Fujitsu DSP that they used on the Model 1 board, to the 2B board using the Analog Devices “SHARC” DSP, to the 2C board using Fujitsu’s updated TGPx4 DSP.

        That only covers the hardware for ingesting display lists and converting it to a series of draw calls that could be handled by the rasterizer hardware. So far, nobody has actually worked out how that part of the hardware worked. People consistently point to ElSemi’s Model 2 emulator as some sort of holy grail, but the reality is that he shared its source code with us folks on the MAME team, and it contains so many game-specific hacks as to be useless. It contains zero insight into how the hardware actually worked.

        If you want the most likely direct predecessor to the Saturn, you want to be looking at their H1 board, which was used for a grand total of 2 known titles: One being Cool Riders, the other being an aquarium-themed coin-pusher. It was based on the SH-2 (albeit only one of them), it had the same SH-1 sub-CPU, it had the Motorola 68000 driving the sound hardware. It was a massively 2D system, having some pretty impressive compression implemented in hardware to maximize the capacity of the fairly expensive ROM chips at the time.

        The only thing that really differentiates Sega’s H1 board from the Saturn was the lack of a second SH-2, the hardware lacking the ability to apply transforms to sprites that would allow for the level of fake-3D that the Saturn had, and the lack of their custom “SCU” microcontroller for system-maintenace tasks like polling the controllers.

        We don’t even have to get into how utterly wrong you are about there “[not being] many emulation options” for the N64, since they are plentiful. The problem is simply that most emulator developers are lazy, and don’t actually want to bite the performance bullet that would involve emulating it accurately. This has nothing to do with the PlayStation or Saturn, because frankly, most emulators for the PlayStation are also wildly inaccurate. They, too, don’t want to eat the cost of emulating it well.

        Unless your intention was to specifically tie Sega’s H1 board to the origins of the Saturn, you’re just plain wrong, and should probably stop posting about things you know nothing about.

        1. Well you’re no fun at parties. N64 and Saturn emulation is pretty rough. And I get it, I’ve read about reverse engineering hardware without any information to begin with. I have the vaguest notion of the lengths people go to to understand undocumented hardware. We’ve got hobbyists lazering chips open to photograph them, emulators like BSNES, it’s all fascinating. I hope to understand it half as well as you apparently do.

        2. You obviously know more than I do. Are there any worthwhile accuracy-first emulators besides higan? I always appreciated Near/byu’s (RIP :C) take that someone needs to have archival quality emulation working *before* original hardware gets hard to find.

    3. It’s really not over-engineered when put in context.

      You’ve got one chip for 3D textured quads. That’s what’s also drawing your sprites. You won’t fill up a lot of your screen with that only, so you’ll need other layers. You’ll leverage another chip for large backgrounds and related special effects. This isn’t much different than the tiles engine and background planes visuals on the previous generation, but it’s got quite a boost in capabilities.

      You’ll need a CPU. Turns out, the SH2 is designed to cascade, so using two, for two cores, is not so much of a stretch. Ideally you’d also provide a better bus for that upgrade too, which unfortunately the Saturn was not given.

      You’ll want some good hardware for great sound too, and you’ll need to drive this with another chip.

      You’ll have to control I/O, meaning you’ll need something for peripherals, with a specific care for the cdrom drive too – this need some finesse, a buffer, some more to alleviate seek times.

      And, well, that’s about it. Down the line, some of this chipsets may be combined into one package – we’ve seen it before, with the Sega 315-5960 for instance. But for a launch unit, you’re at the point the hardware is serviceable.

    4. For what its worth, when the Sega Saturn was launched, SEGA had a total of SIXhardware units it was supporting at the time (Genesis/Megadrive, Master System was still sold in some markets, Game Gear, Sega-CD, 32X and Saturn) and two of those were terrible add-ons for the Genesis. Sega was also focusing on amusement parks and arcades still. Hard for an engineer to do good work when you probably don’t know what the hell you’re working on next.

    5. The linked article explains – for the two Hitachi CPUs, Sega realized their competition’s hardware would be faster and asked for a higher clock speed, but that wasn’t available. But the CPU design supported multiprocessing, so they just added a second one in to give the system more horsepower.

      1. The two SH-2s would have been a lot better, but 2 big hurdles prevented that from happening.

        1) Poor documentation. Almost nobody knew in 94 how to program in parallel. They understood 1 CPU and a ton of coprocessors, but not 2 CPUs. Saturn was the first known home console with 2 CPUs. (People will claim other consoles have 2 CPUs, but they really have 1 CPU and other known CPUs acting as coprocessors. The Saturn had two actual CPUs. Both able to access everything on the system.)

        2) Bus contention.

        Sega did not think of adding a second bus for the 2nd CPU to access external devices. So the two CPUs always fought to get the external resources, which hindered performance. By the time 1997 came around, Sega had put out a library that utilized the second SH-2, but by then it was too late.

    6. They’re thinking “Oh man! This is gonna be great! So fast!…”

      But people that actually make things like this, ahould never write the user manual/instructions.
      Because they already know how it works, they tend to assume that more people know as much, and have faith in their product. Sure! Just turn it on, it’ll work fine. Works fine for us, except when we had those 10,003 glitches, but you can just do what we did. It’ll be working in no time.

  1. For some reason the Wikipedia article link has an override to force the use of the Vector skin, which is not the one I use. I am surprised to find out this is even a thing you can do with a Wikipedia URL!

    1. The Amiga shares more similarity with the Super Nintendo, though.
      Both systems had intelligent chipsets, used DMA transfers and had sampling based sound (RAMpler) or “wavetable” (Paula vs SPC-700).

    2. Spoken like a poor Atari owner… 🤣😉😇

      Before anyone gets annoyed, im joking and reffering to the Atari / Amiga rivelry. Although lets face it, the amiga was the better one hehe 😜💨

        1. The Atari ST was often being used here in Germany, as an alternative to an PC/XT. For getting done real work (Amiga was also beloved, of course, but otherwise).

          In was being used in schools/universities and for DTP (Calamus was popular). And by musicians, because of the internal low-latency MIDI ports (Cubase was popular).

          The high-resolution monochrome graphics of 640×400 was being liked, too.

          The ST w/ SM124 monitor didn’t have to hide from a PC with Hercules graphics.

          The PC-Ditto software emulator and TOS’ compatibility with MS-DOS formated floppies was a bonus, too.
          TOS 1.04 (Rainbow TOS) had increased compatibility, even.

          The Atari ST could be integrated in any x86 PC workplace, thus.

          The Atari ST essentially was an alternative to the Macintosh, which was popular over the big pond at the time.

          Speaking of, there even were Mac emulators for Ataris/Amigas! :D

  2. All I remember was I wanted a Playstation for Christmas and my parents got me a Saturn. When asked why mother said “I saw an article that said the Playstation would randomly break”.

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