An Atari 600XL Talks Composite Video

When we write about the 8-bit era of home computers there is a list of manufacturers whose names are frequently mentioned. Apple, Commodore, Texas Instruments, maybe Acorn and Sinclair if you are British, and of course Atari. But when we mention the last of those names it is invariably in reference to their iconic 2600 games console, it almost passes unnoticed that they also produced a line of 8-bit home computers based upon that success.

[ModPurist] was lucky enough to secure one of the Atari 8-bit computers through bartering with a local game store, an Atari 600XL from around 1983 or 1984, complete with its original box, manuals, cartridges, and a data cassette recorder. But on powering the system up and connecting to a TV a problem emerged. There was something there, but through a lot of noise and very blurry indeed. The solution after a bit of investigation turned out to be quite simple, to bypass the Astec video modulator and apply a composite video modification. Further investigation revealed that the original problem had in part been caused by the unit’s 5V power supply falling short of its voltage, so a further modification was to make a USB lead to allow it to be powered from a modern 5V charger.

This is a relatively simple piece of work, so you might be asking “Where’s the hack?”. The answer lies not in the mod itself, but in the detailed look [ModPurist] gives us at the inner workings of the 600XL, since it’s not a machine we see very often. Having the benefit of 30 years of hindsight and knowing the Atari’s competition quite well, we’d say that compared to some other machines of the era it’s a surprisingly well-designed computer both aesthetically and mechanically.

If your appetite for old Ataris has been whetted by this mod, can we draw your attention to this Atari 800 laptop? Or how about this 800 whose 6502 has been replaced with a 6809?

19 thoughts on “An Atari 600XL Talks Composite Video

    1. It was slow but when was interpreted BASIC ever about being fast? That’s why assembly and BASIC compilers were used to write software which needed to be fast. BASIC is about being easy for non-programmers to learn and use. Atari BASIC does this well with its graphics and sound commands, which BASICs on some other systems were missing, particularly the Commodore VIC-20 and 64 systems. There are also many third-party BASICs available which are backward compatible with Atari BASIC, if anyone decides they need more speed. I will also point out that arrays of strings could be emulated by creating one huge string and subdividing it.

      1. It was slow even by interpreted BASIC standards of the time. If you want a really good (imnsho the best) BASIC, look at BBC BASIC. Extensive device-independent graphics, redirectable streams, procedures etc etc.

        1. I’ve benchmarked almost every 8-bit BASIC out there, including BBC BASIC. It is quite fast and powerful but it’s not the fastest and it doesn’t have the highest FP accuracy. BASIC is for Beginners and is typically interpreted. If you want fast, use a compiler. Atari BASIC is a removable cartridge. Buy another version of BASIC, or even another language, and plug it in instead if it bothers you that much. If you think Atari BASIC’s lack of speed is a “hideousness”, I’d hate to hear what you think of Logo, which is a beautiful language, lying beneath the turtle graphics, but all 8-bit implementations are much slower than the slowest BASIC.

  1. Even though it’s simple, I still would call it a hack :D
    Simply starting the task of modifying a circuit to do as your bidding is sometimes more than people can handle, so thumbs up.

  2. I actually have one of these, mine is quite expanded though:

    Composite and S-Video output
    64K base RAM upgrade (requires replacing 4416’s with 4464’s and soldering 3 wires)
    512K extended RAM (uses PORTB on PIA for bankswitching like most Atari expansions)

    And some interesting goodies hooked up:

    IDEPlus PBI-bus HDD controller with dual-CF adapter which is fully OS-compliant and integrates quite well
    Atari 1050 5.25″ floppy with “Happy” board for true DD on SIO bus
    Atari 850 (4xRS232, 1xParallel) on SIO bus w/ iPocket232 serialethernet adapter

    People don’t give 400/800/XL/XE near enough credit. It was definitely one of the most advanced 8-bit computer platforms to ever exist.

    1. The XE GS was Atari’s second computer to game console conversion.

      The 5200 was a modification of the 400 computer. The plan was to make it easy to port games from the computer to the console but it ended up not so easy because of various changes in the design and software. If only they’d gone with the self centering analog controllers, and a heavier gauge plastic on the flex circuit. I do have an idea for a self centering retrofit for the 5200 controller, but don’t have a controller for measuring and testing.

      OTOH, the XE GS *is* an XE with the keyboard deleted. They’ve been ‘back hacked’ into full XE computers by several people.

    2. Yes, Ataris were, unlike most of the competition, complete machines off the shelf. The most lacking feature was an 80 column text display. Using an 800 as a terminal to a VAX “worked” but was quite annoying.
      I still have an Indus DD floppy drive for my 800, which was quite nice compared to Atari’s offerings—smaller and much quieter, too. Make me an offer… :)
      The impact wheel printer was terrible, as in poor alignment but mostly very fragile and limited ink capability.
      I saw an 850 interface module once back in the day. Should’ve grabbed it. Those things became rather difficult to find. I think the RAM-based driver required to use it wasn’t particularly small, memory-wise (by standards of those days) …true?
      Atari also offered Logo, though I never had it. Pascal required, to my understanding, two floppy drives. Ouch.
      The 800 had four joystick ports, which provided more interfacing potential than most of the other Ataris. I bought the third party modem that connected to a joystick port, and it worked very well (for 300 bps, that is).
      One improvement of the 800XL/1200XL over the 800 was 64k RAM. Without modification, 800s maxed out at 48k.

  3. Composite and somewhat rough S-Video mods are easy on these machines. There are add-on boards available out there that will give you a much better looking signal in the end though. A common issue with the quick and dirty mods and even a lot of the original video circuits on more modern displays is “jail bars” and faint vertical bands on the left side of the screen.

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