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Thread: I wish to create a new DMA/RAM expansion card for the Tandy 1000 line.

  1. #571
    Join Date
    May 2011
    Outer Mongolia


    Quote Originally Posted by RetroGaming Roundup View Post
    if there is a selection of working and compatible hardware the fact that there are incompatible ones can be dismissed in a hobby product like this if a manufacturer like GoPro is doing the same.
    Man, after doing *far* more QA testing in odd moments over the last week than I want to do again for a while I am definitely coming around to the idea that the default assumption at least with 8-bit XT-CF is you should *not* trust a card until proven otherwise, rather than the reverse. I'll update that XTIDE compatibility thread after I collate all the data I recorded on the smartphone camera, but the TL;DR is at least when it comes to CF-lite knockoffs there's a lot of room for incompatibility. Adding disktest.exe's mediatest function to the arsenal helped a lot in finding subtle problems compared to the ad-hoc "just load a big program like qbasic a few times and see what happens" test.

    On the bright side, outside of one asterisk it did turn out the two revs of my particular hardware design do agree about which cards are "bad" and which aren't, although how un-subtle the badness was did vary some between different host adapters and IDE_XT firmware versions and type. (TL;DR, at least with my particular setup it seems like the non-186 "IDE_XT.BIN" firmware is more likely to let a bad card appear to work than "IDE_XTP.BIN" is, although in no tested instance did it make a card that fails with XTP completely error-free.)
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  2. #572
    Join Date
    Feb 2017
    Chilliwack, BC, Canada


    Quote Originally Posted by Eudimorphodon View Post
    ...the TL;DR is at least when it comes to CF-lite knockoffs there's a lot of room for incompatibility.
    That's why I said to note if the card was an "off brand." Sometimes people will skimp on something as basic as bypass caps, and I've learned my own lessons hand-wiring my other card what noise can do, even on an 8-bit board. Doesn't mean every home-brew will be problematic, but it's a data point I figured might be worth collecting.
    My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, and some random Pentium in a Hewitt Rand chassis...

    Some people keep a classic car in their garage. Some people keep vintage computers. The latter hobby is cheaper, usually takes less space, and is less likely to lead to a fatal accident.

  3. #573
    Join Date
    May 2011
    Outer Mongolia


    Quote Originally Posted by blackepyon View Post
    That's why I said to note if the card was an "off brand."
    Ultimately, though, that's the trick here, really. If some failures are because of "analog" problems then really any compatibility list can only apply reliably to one particular *card*, or at least one particular exact schematic and PCB layout.

    In testing across two different host adapters I found my batch of cards fell into three pretty clear categories:

    1: Consistently reliable.
    2: Consistently and reliably unreliable. IE, cards in this category behaved exactly and predictably the same degree of bad regardless of host. (This doesn't mean they were *obviously* bad, necessarily. All the cards in this category will take a format and boot.)
    3: Crazy as ****. The cards in this category don't work, but how they behave in detail covers the spread from "seemingly almost okay, just throwing the occasional error" to "not even recognized by the BIOS". There wasn't a clear pattern between my two host adapters which one worked better with these problem children, and I would even go so far to say that some of these cards would behave differently between power cycles.

    Cards in category 3 are what lead me to believe that my newer host adapter prototype might be "noisier" than my first one, but now I'm not so sure because after testing all the C-A-* cards I saw some examples behave "worse" in what I though was the "cleaner" adapter. Without a "genuine" according-to-Hoyle XT-CF-Lite to test against I guess I have no way to tell if there's something particularly and uniquely pathological in play; these cards might all work perfectly fine in another board.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  4. #574


    Quote Originally Posted by rkrenicki View Post
    The connectors arrived yesterday, and while I have not inspected every single one.. they seem to be perfect. They have a snug fit right out of the package, which I am very pleased with.
    Attachment 57684
    Attachment 57685

    The company I used is called Shenzhen RealRun Electronic Co. They typically have a MOQ of 1000, so I did end up paying a bit more per piece than normal for "only" ordering 250. They have a contact link on their Alibaba page here:

    The part number is: "FH2.54*8.5-2*31P 0.64*0.4 Gold 1U PA6T"

    Otherwise, if anyone wants some small quantities, feel free to PM me here or since some of you know me on facebook, you can contact me there.
    Btw, Rob sent me a few to test and they are indeed excellent - I'll be switching to these when my current stocks of 62 connectors run out.
    My Retro Collection:
    CBM: C64, Amiga 500 x2, 600 & 1200
    Apple's: IIc, Mac SE, LCII, LC630 & Power Mac G3/233 Desktop
    PC's: K6-III+ 500 System + Roland MT-32 & Tandy 1000 EX 640kb, 3.5" FDD, CF-IDE 4GB HDD
    Visit my Tindie store for Tandy 1000 Adapters for EX, HX, SX, SL, TX & TL etc

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