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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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  • Re:Um.... (Score:4, Insightful)

    by Samantha Wright (1324923) on Saturday February 11, 2012 @04:45PM (#39006983) Homepage Journal
    For viewing things. VGA is somewhat nicer than the composite video out that most machines of the age shipped with.
  • Re:Um.... (Score:5, Insightful)

    by realityimpaired (1668397) on Saturday February 11, 2012 @04:49PM (#39007021)

    there's actually quite a community for these old systems, and a lot of people who don't enjoy playing on emulators, or who want to recapture the original experience.

    it's pretty cool that they've managed to do this, though I might prefer a different connection type... my current TV does have a VGA input, but I doubt my next one will.

  • 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.
  • by Anonymous Coward on Saturday February 11, 2012 @05:11PM (#39007187)

    It not excessive. It's about supporting widely available monitors.

  • by 0123456 (636235) on Saturday February 11, 2012 @06:50PM (#39007817)

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

    Which is fine until you try selling a chip or distributing the plans, then the IP Barons come to beat you with a big stick.

  • Re:Um.... (Score:5, Insightful)

    by Mr Z (6791) on Saturday February 11, 2012 @10:37PM (#39008981) Homepage Journal

    Actually, it was 32 sprites, with a limit of 4 to a line. It had collision detection but it was rarely useful. It had a single bit to tell you that any sprite hit any other sprite. To figure out what hit what, you'd have to walk the descriptor list and do the actual computation yourself. (Or, in the case of TI Extended BASIC, the interpreter had to do it for you.)

    On the TI-99/4A, that meant actually accessing VDP memory, since there wasn't much other RAM in the system. That itself was pretty slow, because it wasn't memory mapped for the CPU. You have to write to the VDP's address register, and then do repeated reads after it fetched the byte. Depending on the display mode, that could be as long as 8us during active display (Graphics II mode -- everybody's favorite "bitmap" mode.). Fortunately, the address pointer auto-incremented, so if you were accessing a contiguous structure like the sprite descriptor list, at least you didn't have to keep reloading the address.

    Not that TI Extended BASIC was necessarily able to do that, of course. (Read up on the abomination that was GPL. Not the license, but the interpreted language that much TI software was written in, including TI BASIC.) But if you wrote your own assembly code, you could make that optimization, which is probably how Parsec was able to do its soft-scrolling in the time allotted.

    (Actually, VDP RAM isn't memory mapped on any platform that I know of. But other systems have CPU-addressable memory that you could store a shadow copy of data in at least. The paltry 256 bytes on the TI-99/4A, though, are far from enough in many cases.)

  • Re:Um.... (Score:5, Insightful)

    by hairyfeet (841228) <bassbeast1968@@@gmail...com> on Saturday February 11, 2012 @11:35PM (#39009183) Journal

    I'm sorry you apparently fail at reading comprehension so allow me to break it down. What you have was NOT consumer crap, what you have was designed for business and engineering which had waaaaay better quality parts. the caps and chips used in CONSUMER grade crap was then as now simply not up to the quality of professional instruments which is why we have workstations and desktops with the desktops having significantly lower quality caps, PSUs,fans etc.

    We're talking about stuff built for kids in the early 80s and you are talking about HP back when they were THE scientific brand, I'm sorry pal but you couldn't be any more off base if you actually tried and those that marked you interesting obviously don't know how big a quality difference there was between HP and brands like Coleco whose other claim to fame was fricking cabbage patch dolls.

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