An Atari Graphics Chip, Ready For You To Build

The most notable of the home computer and console hardware from the 8-bit golden era didn’t get their impressive sound and graphics from off-the-shelf silicon, instead they relied on secretive custom chipsets to get the edge over their competitors. Unfortunately for vintage gaming aficionados, those chips are now long out of production and in many cases there’s little information to be had about their operation.

Which makes discovery of the schematics (PDF link) for the “Tia Maria” graphics chip found in the Atari 7800 console an unusual occurrence, and one which should be of special interest to the emulation community. They can be found alongside the rest of the Atari Museum’s 7800 information.

That such a useful document is available at all is due to a lucky find in a dumpster following the demise of Atari, when a treasure trove of documents was discarded. It seems that the existence of these schematics has been known within the Atari community for some time, and we expect before long this information will find its way into FPGA implementations of the 7800; especially since the system features nearly complete backwards compatibility with the massively successful Atari 2600.

When that happens we hope we’ll be able to bring it to you, but it’s not the first time someone’s made an Atari on an FPGA.

Via RetroRGB

Header image: Bilby [CC BY 3.0]

27 thoughts on “An Atari Graphics Chip, Ready For You To Build

  1. The 7800 uses this chip to create 7800 mode video but the system also contains a TIA chip for sound and 2600 compatibility.

    So the Maria chip itself would not net you 2600 compatibility nor would your system have sound

    1. That’s a good idea. The Visual6502 project shows how they reversed the 6502 by etching, photos through an optical microscope a camera and some software. They had planned to reverse the TIA (2600 video) as well.

      For more modern designs that are too small check out the article “X-Ray Tech Lays Chip Secrets Bare” on IEEE Spectrum.

  2. “That such a useful document is available at all is due to a lucky find in a dumpster following the demise of Atari, when a treasure trove of documents was discarded. ”

    And landfills. Definitely check those.

  3. I remember how I had a C64, where every little thing was documented (well, as far as possible). And having an Atari 800XL, thinking that it was inferior because it did not have any sprites. But learning only after I sold the Atari 800XL again that it actually had something called player/missile graphics, which were in fact sprites, but that it was just undocumented and people only found out that they were in there by reverse-engineering Atari’s code.

    So, the lack of openness caused Atari’s demise. I am 100% positive of that.

    1. I think you needed to look a little a harder at the time. There was plenty of detailed technical material available for purchase at the time, even to users and not just developers. The player missile graphics was not undocumented and was one of the items covered in a major computer magazine’s 3-part series on the then incredibly innovative Atari 400/800 custom chip sets. That’s what led me to buy one.

        1. 100% postive of that? Truly, you must do a bit of research and learn actual history. As Winston said, the architecture and how to use it were extremely well documented. And the Amiga (whose main chips were designed by the same people who designed the Atari 8-bit chip sets) came way later and were the logical descendants of the 8-bit chips. And as Winston said, mismanagement was the demise. I’m 100% positive of that.

          1. Yes, 100% positive. I BOUGHT at the time some of the documents now found in PDFs and performed assembly language programming and the technical reference manual to do compatible hardware work.

        2. At the time there were dozens of computer makers. All the CPM makers, Timex, Wang, Tomy, Mattel, Ti, Magnavox; for example. None of them survived because none were handed keys to the IBM computer monopoly the way that Microsoft was. It was simply not possible to survive because none of them could bring the software developers or the market penetration that selling PC-DOS to businesses via the IBM sales force could. Once adopted by businesses, workers could justify a home machine to get a leg up and get the software by pirating it from work. Apple hung on because they had gone to schools and rich parents bought them for their kids; they got developer support before the MS-DOS flood swept the rest away and nearly went under. Apple had a short lived win when they had Visicalc, but then it wasn’t long before everyone had the same.

          Even the best decisions were losing decisions. The only terrible choice was IBM not buying Microsoft outright.

      1. Thanks, I just searched quickly for those articles, probably the january 1981 editions of both “Compute!” and “Byte” magazines, which first made these technical informations publicly available, about a year after the Atari 400/800 were released to the market (…and 6 years before the Amiga 500 was presented).

        This wikipedia page of the resulting book compiling the Byte series, contains the links to each original articles viewable on :

    2. PM graphics were on most of the marketing materials at the time, and not that long after that computer magazines and books had all kinds of programming info, including player-missle grapics, display list interrupts, pokey sound programming, etc.. All of this was years before the 800XL or c64 existed.

      The closed approach Atari took was short-sighted, but it didn’t take long at all for the information to be freely available, and wasn’t a reason for the failure of the line.

      Blame the many poor decisions made by Atari management, and rampant piracy that caused publishers to move to more lucrative platforms.

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