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TMS9918A Retro Video Chip Reimplemented In FPGA, With VGA Out 126

Posted by timothy
from the disintergrated dept.
acadiel writes "Matthew H from the AtariAge.com TI-99/4A forum has finalized a design of a TMS 9918A replacement (with VGA out) for classic computer systems such as the ColecoVision, TI-99/4A, SpectraVision, MSX1, SpectraVision 128, and Tomy Tutor Home computers. This hardware project replaces the native video controller on these classic systems and enables them to have VGA output for the first time." (It's just under $100 to order one.)
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TMS9918A Retro Video Chip Reimplemented In FPGA, With VGA Out

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  • he'd better do an HDMI version quick as VGA seems to be on the way out as a connector :-P

    • by 0123456 (636235) on Saturday February 11, 2012 @04:56PM (#39007071)

      he'd better do an HDMI version quick as VGA seems to be on the way out as a connector :-P

      Except HDMI is a closed standard and buying HDMI chips requires signing over your first-born to Satan.

      • Re: (Score:3, Informative)

        by cb88 (1410145)
        then just implement DVI-D over HDMI ... so you don't have to bother with the DRM. Check out the wikipedia article I imagine there are some kinks but HDMI is mostly backwards compatible with DVI-D And I have real world evidence as well.. Pandaboard does DVI-D for the very reasons you mentioned and it works just fine with a couple TV's I have tried that said it was picky one one monitor I tried though it seemed to be a kernel issue as one kernel would boot up on HDMI the other on DVI so had nothing to do wit
        • by windcask (1795642)

          This sounds like a good plan. Most people are going to want to be playing these systems on their TVs, not computer monitors, and there aren't a ton of TVs still being manufactured with VGA-in.

          • Are you in Europe? (Score:2, Interesting)

            by tepples (727027)

            there aren't a ton of TVs still being manufactured with VGA-in.

            Just about every LCD TV that I've seen in (U.S.) stores has a VGA input. It might be the case that you live in Europe and your local TVs include a SCART port instead. I'd bet the actual video processor in such TVs can sync to both 480i SCART and 480p-1080p VGA.

      • by KiloByte (825081) on Saturday February 11, 2012 @05:35PM (#39007339)

        Except HDMI is a closed standard and buying HDMI chips requires signing over your first-born to Satan.

        As someone who used to worship Satan as a kid (yeah, stupid), I resent that remark. Please do not insult Satan by comparing him to a vile media consortium.

        • by Anonymous Coward

          Doesn't Lucifer actually mean "bearer of photoluminescence"?

          • by celle (906675)

            "Doesn't Lucifer actually mean "bearer of photoluminescence"?"

                So his avatar is a nuclear explosion.

                Bright enough for you?

      • Except HDMI is a closed standard...

        ...that is freely downloadable from Chinese web sites... :]

      • by rthille (8526)

        Satan (assuming he shows up to take him/her) is welcome to my first-born. I'm unlikely to have one, and wouldn't want it if I did. Now the woman actually pushing the baby out may have other ideas...

      • I'm not sure I want to put up with the first-born of a bunch of /. techies...

        .
        Regards,

        Satan

    • by mattventura (1408229) on Saturday February 11, 2012 @04:57PM (#39007077) Homepage
      If they only had composite to begin with, anything above VGA is completely excessive. These machines are never going to be outputting 1080p.
    • Shouldn't adding a VGA to HDMI converter take care about that one?

      • by Joce640k (829181)

        Missing the point: HDMI is all digital....and why should you need an add-on converter?

  • by JoeCommodore (567479) <larry@portcommodore.com> on Saturday February 11, 2012 @04:56PM (#39007069) Homepage

    Of all the chips that one on the Commodore 128/128D is a pain to convert to anything modern as it uses the old CGA/RGBI interface. All the CGA adapters ive found dont handle the intensity signal, they are more RGBA compatible.

    • by Anonymous Coward on Saturday February 11, 2012 @06:01PM (#39007527)

      But this is not a big problem -- there's dead-simple passive analog circuits (e.g. [google.com]) to do a passable conversion, and if you want to fix the dark-yellow/brown issue, that's not hard either.

      RGBI signals in CGA are TTL, so converting to analog RGB is as simple as connecting them to the address lines of a suitable 8-bit PROM (or SRAM, in which case you'll want a battery to retain memory) programmed with appropriate RGB values, and three 2-bit ADCs on the output (0=0v, 3=0.7v for VGA).

      You want to program the ROM/RAM as follows, assuming I as MSB (note color 6, brown, deviates from the expected 220):
      N | RGB | xxRRGGBB
      --+-----+---------
      0 | 000 | 00000000
      1 | 002 | 00000010
      2 | 020 | 00001000
      3 | 022 | 00001010
      4 | 200 | 00100000
      5 | 202 | 00100010
      6 | 210 | 00100110
      7 | 222 | 00101010
      8 | 111 | 00010101
      9 | 113 | 00010111
      A | 131 | 00011101
      B | 133 | 00011111
      C | 311 | 00110101
      D | 313 | 00110111
      E | 331 | 00111101
      F | 333 | 00111111

      Or use a 16-bit ROM and wider DACs, and you could customize each color to exactly match your old 1902.

      Seems a PCB with a preprogrammed ROM, DACs (could be as simple as R-2R ladder), and a scan doubler IC, should be much cheaper than a $100 replacement video chip.

  • by Guppy06 (410832) on Saturday February 11, 2012 @05:34PM (#39007333)

    classic computer systems such as the ColecoVision

    This word, "computer," I do not think it means what you think it means...

    /former Adam owner

  • I have ColecoVision and a black and white TV.

  • Why not put the entire Atari 800 in FPGA, in a PC, and use SVGA (and higher) output? That sounds like a really fun turn that "classics emulation" could take.

    Are Atari computer game ROMs and software binaries still copyright restricted?

    • Most home computers have analog circuits too - most notably for reading paddle controls, which FPGA's cant handle. And yes, folks do use paddles (also applies to some mice, and mini tablets like the Koalapad.

      • Most home computers have analog circuits too - most notably for reading paddle controls, which FPGA's cant handle. And yes, folks do use paddles (also applies to some mice, and mini tablets like the Koalapad.

        OK, a FPGA and a 555 timer chip.

      • by Osgeld (1900440)

        everyone except the tandy series used a 555 timer based circuit for paddle and analog joystick control, nevermind its trivial to do analog even in 1980

      • by Doc Ruby (173196)

        ADC seems pretty cheap, straightforward and common in the kind of FPGA board you'd put in a PC and run an Atari simulation on.

        The real question is whether ANTIC, POKEY and other complex circuits are available as FPGA cores, since a 6502 core is available [6502.org].

  • Even more surprising than that: There's an active TI-99/4A group? Really? Is Bill Cosby a member? That was my first home computer and so it'll always have that special place in my memories, but that thing wasn't very useful when it was still current. I can't imagine trying to do anything useful with it now.
    • I loved my TI99/4A ... I still have it somewhere. I didn't realize there was an active group for it, but its still an awfully advanced system for its era.

      • by drussell (132373)

        Yes, it was.. Real 16-bit even, though only the stock 256 byte system RAM (yes people, 256 BYTES) is on the 16 bit bus, but it's SRAM and runs at full processor speed (like L1 cache in todays processors)... I have an extra 32K of ram installed on one of mine directly on the 16-bit system bus... That would have cost a fortune back then, now it's just a few chips from the junk box! :)

        • by Mr Z (6791)

          Did you disable the wait states for the extra 32K RAM? I seem to recall that it did an address decode, and if the access was to the 8-bit bus and not to the VDP, it threw in a ton of wait states.

        • I had the 4K expansion with the voice output system for mine, cost an additional $400 or something. It was pretty crazy.

    • by drussell (132373)

      That was my first home computer and so it'll always have that special place in my memories, but that thing wasn't very useful when it was still current. I can't imagine trying to do anything useful with it now.

      You must not have had a PEB... With the Peripheral Expansion Box the 99/4A was capable of similar performance to the early PCs.

      Even more surprising than that: There's an active TI-99/4A group? Really?

      Yes, there are those of us still active in various old computer projects, building IDE disk interfaces, etc. to allow easy use of these fun old boxen.... I've built my own CROM/GROM emulator for the TI (someone else designed an IDE interface but I haven't built one for myself yet) and I'm currently designing and building an IDE disk interface for the old WANG 2200 minicomputer line

  • My first PC was a TI 99/4a. I really really wish I had kept it. It's probably in a landfill somewhere by now. :(
    • by drussell (132373)

      Yes, I don't have my original either (parents threw it away long ago without my knowledge) but I have 3 I picked up on eBay for a song... Go get one and a Munch Man cartridge and have fun... :)

    • by nurb432 (527695)

      Sorry to hear that.

      Really. It was an overpriced, dismal performing machine that while had a lot of technical promise, it was severely handicapped and was not worthy of being designed by TI.

      There is a reason they could barely give them away towards the end, while other 8-bit machines were still selling like hotcakes.

      And yes, i had one when they were new and its still part of my collection, and it NEVER gets turned on, because well, to be honest, it sucked.

      • by nurb432 (527695)

        Grrr /. really needs a 'edit' feature.. I know it was 16 bit, but was during the 8 bit market.. Thats what i meant above.

  • it used a TMS9928A, hand over your nerd card now!

    ok its the same chip just with RGB output though the Coleco didnt use RGB, which has really confused me, most of the computers use the 18 which spits out compostite, where RGB would be preferred, the Coleco used an RGB chip and summed it together into composite, talk about ass backwards.

    • by Mr Z (6791) on Saturday February 11, 2012 @10:43PM (#39009003) Homepage Journal

      It's not really RGB output, but rather Y, Y - R and Y - B luma/color difference signals -- actually frightfully close to S-video. But I'm pretty sure they had an app note back in the day that showed how to sum those to get RGB almost trivially.

      The reason they went with the 9928A (and later 9128A) was to avoid the "rainbow effect" that was is prominent on the 9918A. See, the 9918A didn't flip the chroma carrier field-to-field, which leads to reinforcing chroma errors. That's also why you couldn't use the EXT VIDEO input on the 9918A to mix with arbitrary video sources (say, for a video overlay), but you could use it to daisy-chain VDPs to get more sprites and such.

    • by drussell (132373)

      This board also replaces the TMS9928:

      "The F18A is a pin-compatible replacement for the TMS9918A, 9928, and 9929 Video Data Processors"

  • If only I can find all my old TI-99/4A tapes, I can play my old Pac-Mac knockoff.

    I'm tired just thinking about it, and bored already.

  • Heh! Perfect! I have three TI-99/4A machines and one has only B&W output because the 9918 is frizzafrazzed.. This will let me "upgrade" that one to VGA output! Sweet... lol

    • by Osgeld (1900440)

      you know recycled stock of these things come up all the time for less than 10 bucks, the only advantage here is the monitor bandwidth if they didnt fuck up their sampling, which is very easy to do

      • by drussell (132373)

        you know recycled stock of these things come up all the time for less than 10 bucks

        Oh, I know... I just never bothered because I have three 99/4As and it still works, just not color and could be useful for parts if one of the ones I actually play with (one is original, one is modded) have a problem. Now if I buy one of these, it's $10 saved by not buying a 9918. :) I had always thought of getting one of the later Yamaha chips like used in the Geneve, can do a little board for one of those with 128k or 192k of video RAM and do whatever it was, 512x512 graphics... I don't have a Myarc so

  • by ogdenk (712300) on Sunday February 12, 2012 @12:54AM (#39009433)

    http://spiflash.org/block/15.html [spiflash.org]

    The VBXE video board for Atari 8-bit XL and XE machines. Will do 15khz RGB and VGA out and coexists with and extends the original video coprocessor chips (ANTIC and GTIA) providing a blitter and extending the color palette. Enhanced sprites too and more stuff. The Atari graphics chipset was much more programmable and flexible than this thing though every machine deserves to still have modern video output options. The Atari 8-bit is kinda like a baby Amiga in ways.

  • from wikipedia 2012.02.12 'Planned Obsolescence'

    In Democracy in America (1840), Alexis de Tocqueville noted the rise of planned obsolescence in the United States: "I accost an American sailor, and I inquire why the ships of his country are built so as to last but for a short time; he answers without hesitation that the art of navigation is every day making such rapid progress, that the finest vessel would become almost useless if it lasted beyond a certain number of years."

    Now I deal in used VGA and SVGA

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