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

  1. Default

    This is just wonderful stuff, seeing new cards for this PC! I have a few OEM memory expansions, and an aftermarket one, so I don't *need* a new production one but I am anxiously anticipating getting my Eudimorphodon special in the mail once he gets these sorted!

    I am sure this is well known, but just in case, I ran across an online copy of the technical manual for the HX and it is absurdly detailed. https://www.manualslib.com/manual/13...page=62#manual

  2. #192
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    Quote Originally Posted by RetroGaming Roundup View Post
    This is just wonderful stuff, seeing new cards for this PC! I have a few OEM memory expansions, and an aftermarket one, so I don't *need* a new production one but I am anxiously anticipating getting my Eudimorphodon special in the mail once he gets these sorted!

    I am sure this is well known, but just in case, I ran across an online copy of the technical manual for the HX and it is absurdly detailed. https://www.manualslib.com/manual/13...page=62#manual
    We've got the technical manuals for the EX/HX already. One thing we've found is that the tech manual for one model will include minute details they share in common that another manual will leave out.

    If you happen across the tech manual for the Tandy 1100FD though, I'd be grateful. It's got two internal expansion headers, one for a small card (what I presume to be a modem), and the other for an internal HDD of unknown type, and I've been unable to locate any information yet. I'd like to make a CF card board for it, but I suspect that it uses XT-IDE (not to be confused with the XT-IDE Universal BIOS), which predates and is incompatible with what we'd normally think of as IDE. But if it DOES use standard IDE, then a CF card interface could be relatively simple, depending of what drive geometry the onboard BIOS can recognize. Fortunately, it comes with 640KB RAM right on the board, so there's no concern there.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, 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. Default

    I have a box full of 1110HDs, very similar. One of my favorite computers and my first laptop, I actually got yelled at in the Army for having one because the only people who were "supposed to have one" were higher ranking officers FFS. About 10 years ago I had one running great and then its internal HDD died, I haven't seen a working HDD in years now and I would love to revisit this. It would probably not be that hard to look up the specs on the drive or controller chip and figure out what it is.

  4. #194
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    Quote Originally Posted by RetroGaming Roundup View Post
    I have a box full of 1110HDs, very similar. One of my favorite computers and my first laptop, I actually got yelled at in the Army for having one because the only people who were "supposed to have one" were higher ranking officers FFS. About 10 years ago I had one running great and then its internal HDD died, I haven't seen a working HDD in years now and I would love to revisit this. It would probably not be that hard to look up the specs on the drive or controller chip and figure out what it is.
    So far as I can tell, all the large ICs on the motherboard are FPGAs or custom ASICs. That's why I was hoping to find a technical manual. If nothing else, I'd have schematics to go on, so I can at least tell what's what. Failing that, I could always bodge-wire an "ISA"-like interface straight from the CPU and address/data latches, but I'd like to avoid that if the connectors serve that function.

    Anyways, that's a topic for another thread.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, 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.

  5. #195
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    I've run into one little glitch that had me go way back in the thread and dredge this up:

    Quote Originally Posted by blackepyon View Post
    Well, I rigged up a PLUS to breadboard lead pack, hooked up a 512K chip as you suggested....
    ...
    And it works!
    It even passed an extended memory test.
    Attachment 53974
    Out of curiosity, what version of Check-it! were you running the memory test from? I've found that I don't seem to be able to get a completely error-less run of the "Extended" RAM test; it will inevitably record at least one error on the "Parity" check... which is kind of fascinating considering the Tandy doesn't have Parity RAM. The errors are not reproducible in terms of location, and further, the errors are sometimes recorded in the range covered by the *Big Blue RAM onboard*, not the expansion memory. Is there another good RAM test for XTs that would be worth running for sanity's sake? For what it's worth I haven't had any mysterious crashes or anything with any of programs I've tried that exercise the expansion RAM.

    The one physical possibility I can think of is that some of the sockets on my test board are pretty thrashed from having wire jumpers stuck in them, perhaps there's a slightly intermittent connection randomly putting some kind of glitchiness on the bus. I'll need to replace them eventually, or just solder up another board, once I have any other possible bodges worked out.

  6. #196
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    I was using CheckIt 3. There's also a possibility that some of your onboard chips could be bad. The reason I started this project to begin with was because I was encountering RAM errors, and it looked for all the world like they were on the expansion memory until I changed out the 8 memory chips on the motherboard. CheckIt 3 needs more than the base 256K though, which is why it took me so long to narrow it down. Knowing that the machine maps the expansion memory before the onboard, it now makes sense what CheckIt was reporting to me when I was getting memory errors.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, 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.

  7. #197
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    I hate to invoke the somewhat overused "bad caps?" canard, but maybe its applicable given the errors aren't reproducible. *Sigh* The joys of thirty year old hardware.

    I guess here's another reason why you building up your copy of the board is a useful exercise.

  8. #198
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    In my case, simply replacing the onboard chips solved the issue, and I tried this set of chips on another motherboard to be sure (I ended up buying a spare HX motherboard for an unrelated screwup that I might have mentioned earlier). While old X-class capacitors from this period are notorious for going bad and releasing the magic smoke (which is why I recommend replacing those before even powering the machine on when you first get it), I've never seen a bad electrolytic cap from this time period, though that could change as my collection grows.
    My vintage systems: Tandy 1000 HX, Tandy 1100FD, Tandy 1000 RSX, 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.

  9. #199
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    Back to this again after a vacation hiatus...

    I've succeeded in verifying that the SMWCLOCK.COM binary in the Tandy archives can set/read a Maxim DS1315 mapped at C000. Here's the program running on my Tandy 1000 EX fitted with the prototype combo RAM/Calendar/Flash board:

    smwclock.jpg

    This is it setting the time after a cold boot; no special command line switches or anything were needed, it just finds the chip with no drama, and although I've only had it running for about half an hour it does seem to keep reasonably accurate time. There's a minor cosmetic Y2K bug in the program's output but the DOS DATE command shows the correct value.

    Getting it working was a huge hassle because I was a bonehead and accidentally ordered surface-mount DS1315s instead of thru-hole from a very cheap Chinese eBay listing. At least the chips are good, but I really put the poor victim I installed through the ringer adapting it to the board. Witness the pain here:

    ds1315.jpg

    It's the tape-covered chip under the battery, of course.

    So, yeah, it looks like it's perfectly legit to incorporate one of these chips into a Plus add-on card.

    In the not so good news I'm having much less luck with the Flash chip I installed. I tried to make the board compatible with the lo-tech CompactFlash Adapter rev. 2b, with the exception that the board gives a whole 64k starting at C000 to the flash chip instead of 32k at C800. (The documentation implies at least that a 64k flash should be supported, though.) I tried padding the 8k IDE_XT BIOS file on the Lo-Tech site with a leading 32k's worth of zeros and running "flash padded.bin C000", but it hangs indefinitely at "Calibrating delay loops".

    I did try one of the flash chips I ordered (stupidly) from a Chinese eBay listing, I have a couple from Digi-Key, I'll swap it out and see if it changes anything. But it's still good news about the calendar chip.

    (Granted it could be my s*** soldering on the calendar chip is the problem, being that chip select for the flash chip passes through it.)

    Edit: Also, I've noticed an oddity. I tried running the extended RAM test from Check-It version 2 instead of Check-It version 3, and my machine passes that reliably. I'm not sure what to think about that, other than the fact that when it fails it's always blaming "Parity", which is odd because the Tandy 1000 series doesn't have Parity RAM. According to the Tandy manual the I/O port addresses the PC uses for signaling parity errors (and enabling/disabling reacting to them) are used for other purposes or reserved in the 1000EX, so... yeah, I don't know what's up, whether the test is just getting spurious results from tickling registers that don't do what it expects, or if the version 3 test is somehow hitting a legitimate edge case version 2 doesn't.
    Last edited by Eudimorphodon; August 10th, 2019 at 10:35 PM.

  10. #200

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    Speaking of DS1315's, I got my 20 of them from the cheap seller I found and not a single dud amongst them! 100% working! They are chip pulls but they've done a decent job of refurbishing them IMO.

    here's the link:

    https://www.aliexpress.com/item/3283...AbTest=ae803_5
    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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