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

  1. #511

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    I just wish that D-sub punch dies were not $600+ a piece. I have two different projects that could use a DA sized and DE sized punch, but I do not have $1200 to spend on them.

  2. #512
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    Yeah, that's what the drill and a dremel are for.
    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. #513

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    Quote Originally Posted by blackepyon View Post
    That might not be a bad idea, if we can agree on a common design. Probably a three-hole blank plate, with right-angle arms to mount to a 100mm board, and holes tapped for 6-32 threads. That way, you just get out the drill and dremel to modify them as needed for the application.

    Well, my boards just shipped, and should be here in a week or less, so I'll see if I got the measurements right.
    I have some ISA proto cards whose brackets have a break-out section (kinda like you see on electrical junction boxes) that's set up so you can break it out for different sizes of d-sub connector. It's a little ugly-looking, but something like that might be best? It's past my bedtime for now, but I'll try to remember to go up and take some pictures tomorrow evening and attach them.

    Barring that, I think if I was gonna cut very many with a dremel, I'd try to find someone with a CNC mill instead. =:3 Hmm although I guess if it didn't have to be exactly D-shaped, it could be done with only two plunge and cuts on a manual mill anyway.
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  4. #514
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    Quote Originally Posted by bladamson View Post
    I have some ISA proto cards whose brackets have a break-out section (kinda like you see on electrical junction boxes) that's set up so you can break it out for different sizes of d-sub connector. It's a little ugly-looking, but something like that might be best? It's past my bedtime for now, but I'll try to remember to go up and take some pictures tomorrow evening and attach them.

    Barring that, I think if I was gonna cut very many with a dremel, I'd try to find someone with a CNC mill instead. =:3 Hmm although I guess if it didn't have to be exactly D-shaped, it could be done with only two plunge and cuts on a manual mill anyway.
    Knockouts would need a punch if you're getting them fabricated, which drives the cost up. Besides, knockouts are only really useful for those particular connectors.
    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.

  5. #515
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    Well, I've been having some fun with in-depth testing. So far I think my hardware is actually just fine, but it's kind of amazing some of the machine-specific quirks I've run into.

    Does anyone who's keeping an eye on this thread happen to use an Ethernet card in their EX/HX using whatever kind of adapter you've made, bought, or otherwise magic-ed into existence? I'd be curious to hear what you're using and what hardware resources you've assigned it.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #516
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    Quote Originally Posted by Eudimorphodon View Post
    Well, I've been having some fun with in-depth testing. So far I think my hardware is actually just fine, but it's kind of amazing some of the machine-specific quirks I've run into.

    Does anyone who's keeping an eye on this thread happen to use an Ethernet card in their EX/HX using whatever kind of adapter you've made, bought, or otherwise magic-ed into existence? I'd be curious to hear what you're using and what hardware resources you've assigned it.
    I think EEGuru was trying to get a custom built one going at some point (check the first page of this thread). There's plenty of hardware I/O availible, but only three IRQs to choose from, 2,3 & 4, as that's all that's been routed to the expansion header. IRQ 5 is used for the vertical refresh circuit (because reasons), and IRQ 7 is for the onboard parallel port, so they didn't bother routing those to the header. A few "unused" pins on the expansion header are instead used for DMA control functions to the MB from the DMA/RAM card that aren't normally available on an expansion bus, which is why I wanted to reverse-engineer that T512 card (my next project, once I verify that my PLUS-IDE board is working).
    Last edited by blackepyon; November 14th, 2019 at 06:19 AM.
    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.

  7. #517
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    You may have seen my other thread about getting an Ethernet card for my EX, which is what triggered the question about what slot resources people are actually successfully using in their Tandy 1000s. It's starting to feel like the limited IRQ selection might possibly a bigger strike against completely "gonzo" builds for these machines than no DMA might be. I do find myself wishing that IRQ7 at least came to the slot connector; it was pretty common practice back in the day to piggyback onto that and just accept you weren't going to be printing and whatever-else-ing at the same time.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  8. #518
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    Quote Originally Posted by Eudimorphodon View Post
    . . . which is what triggered the question about what slot resources people are actually successfully using in their Tandy 1000s.
    The second PC card that I ever bought for my 1000SX back in '87 or so, was a 300 baud dial-up modem - don't remember the brand, 'Harry Swartz' I guess, and the first was a bus mouse (still works). IIRC, it had some DIP switches and a slip of paper on how to set it up. It always worked and slow wasn't a problem because who could afford anything faster back then for home use? It was stunning to be able to connect to some board and actually send stuff back and forth. I had some job related experience with acoustic couplers back in the early 80's, but this was way better. I don't think IRQ's present much of problem with 1000's even with a HD. I still have a WD 8-bit MFM controller which has been modified for the early 1000 by altering the IRQ assignment. Somewhere, I still might have the write-up on how to do it, and it involves simply cutting a trace and soldering in a jumper. Got this 'fix' from tech who worked for WD and moonlighted at a RS store. Turns out the SX didn't require that mod as the IRQ's are selectable on the motherboard. (something to do with IRQ2 & IRQ5).
    Surely not everyone was Kung-fu fighting

  9. #519
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    Quote Originally Posted by Agent Orange View Post
    ...Turns out the SX didn't require that mod as the IRQ's are selectable on the motherboard. (something to do with IRQ2 & IRQ5).
    That's interesting. It looks like the SX had IRQ 2-7 present on the expansion bus, but had jumpers to disable the interupt on the onboard video, FDC, and printer port. Presumably to allow add-on cards in their places. Question is whether or not the onboard devices work without the interrupts?
    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.

  10. #520
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    Quote Originally Posted by blackepyon View Post
    That's interesting. It looks like the SX had IRQ 2-7 present on the expansion bus, but had jumpers to disable the interupt on the onboard video, FDC, and printer port. Presumably to allow add-on cards in their places. Question is whether or not the onboard devices work without the interrupts?
    Back then you were limited to the smaller 8-bit cards because of the 1000's short chassis. I never used a serial port on my SX as I went with the bus mouse. IRQ's were never much of a problem because you were pretty much constrained as far a peripheral or add-on card size. The printer was easy as it has its own dedicated parallel edge connector. Some outfit, I think it was 'Leprechaun', used to advertise an expansion case in 80 Micro for about $700. I don't think it was a very big seller. Since you were limited to 5 slots you had to do some planning. I had an EGA card, bus mouse, RTC, WDC, and of course - the modem. Also, there was a mono audio card that I occasionally swapped in and out with the modem. That's pretty much the way it is today, but the RTC is now piggybacked on the BIOS chip and the HD is a CF running off one of Hargle's first XT-IDE cards. One of the 5.25's has been replaced with a 3.5 and the EGA has given way to a garden variety 640 x 480 VGA. THe CPU is a V20 and there is a 80387 on-board as well. The very first mod to this box was to bump the RAM up to 640 KB. The original WD controller and ST-225 still function but are put away for safekeeping. My grand kids couldn't care less about this stuff but the latest crop of great grand sons show some promise.
    Surely not everyone was Kung-fu fighting

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