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

  1. #21
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    Quote Originally Posted by eeguru View Post
    As long as it's combinatorial only 'L' variant. If its an 'R' or 'V' registered variant (containing flip-flops), it becomes more difficult. If the security bits are not set, you could just read the fuse data out with a programmer.
    Tandy appears to have only used 82S153s when they needed programmable logic in the 1000 and its initial add-on boards. They are simple combinatorial logic chips that can be easily replaced.
    My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

  2. #22
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    Quote Originally Posted by eeguru View Post
    If you are interested, I can post the schematics online as a starting point for you. Or with enough poking, I could pick both designs up again and push forward.

    I would have released a PLUS memory expansion a long time ago (I have 6-8 other PLUS cards designed but not produced) if I could find a suitable solution to the high-stacking shrouded 62 pin IDC connectors. But, the ultimate board would be a two card stack with it's own mating system that would provide an upward facing PLUS connector for a 3rd card of choice. I was thinking IDE (or SD card), RAM, RTC, MPU-401, 1x serial, and NE2000.
    Having just become the proud owner of a memory-expansion-less 1000 EX count me as someone who would be thrilled if you (or anyone) were to pick up this ball and run with it! I've just started looking for possible solutions to this issue and I've seen a number of mentions of the possibility of making a direct port of the JR-IDE board (combo memory+IDE) that could fit the Tandy systems. If you ever feel like laying that out I'd love to take a crack at getting a PCB from a board mill and populating it, if necessary.

    A serial port and RTC would be an excellent bonus, of course.

  3. #23

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    Quote Originally Posted by Eudimorphodon View Post
    Having just become the proud owner of a memory-expansion-less 1000 EX count me as someone who would be thrilled if you (or anyone) were to pick up this ball and run with it! I've just started looking for possible solutions to this issue and I've seen a number of mentions of the possibility of making a direct port of the JR-IDE board (combo memory+IDE) that could fit the Tandy systems. If you ever feel like laying that out I'd love to take a crack at getting a PCB from a board mill and populating it, if necessary.

    A serial port and RTC would be an excellent bonus, of course.
    There is another option:

    https://www.tindie.com/products/Cybe...sa-riser-card/

    +

    https://texelec.com/product/lo-tech-1mb-ram/

    +

    any half height dual serial card

    +

    https://www.tindie.com/products/Cybe...ex-smartwatch/ (I'm out of DS1216's atm tho)

    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

  4. #24
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    I did see that, and I guess that would work for chose-any-two-of RAM, IDE, or serial, and totally don't get the idea I'm discounting your product...

    But, well, it would still be great to have a single card for it at least two of those, like the JR-IDE does for the PCjr. Or... crazy idea: have you considered the idea of making a version of your riser that has a RAM expansion? When looking through eBay for Plus memory cards (ha!) I ran across this bizarre thing someone built. (And total respect to you if you're a member of this forum, it's awesome.) Here's a link to the auction:

    https://www.ebay.com/itm/Duo-Slot-51...-/273735338008

    The card consists of a 512k SRAM chip on a riser with two slots for adding the same cards we might want in an EX/HX to the "wasted" space in an original Tandy 1000. Obviously the clearances are tighter in an EX (I don't have the machine near me to tear into it and measure), but... what if there was *just* enough space to fit an SRAM on there along with the slots?

  5. #25

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    No dramas, my stuff is made as part of my hobby so I dont mind if folks want other solutions.

    I did reach out to the maker of that board and asked if I could use his schematic but he never replied unfortunately.

    That said I am working on a Riser card design using Jame's (of lo-tech fame) 1 MB board as the base design ... however it's overkill for our needs and I'm working on simplifying it .... I cant provide any guidance as to when it'll be ready unfortunately (just started a new more senior role and time poor atm).
    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

  6. #26
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    Yeah, most of us are just fellow hobbyists who just want to see this stuff made. Problem is that not everybody has the time (day jobs, family, whatnot). Still want to get that made eventually.

    As for that memory board, I've heard that lo-tech 1MB card apparently works in the Tandy 1000 EX/HX just fine with dJOS's PLUS riser, so that should at least get you by until one of us can get some PLUS boards going. I don't know if the EX/HX support Upper memory blocks or not, and the motherboard has 256K built in, so you need about 384K of that 1MB.
    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. #27
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    How rare is the memory board for the 1000 desktop that gives you full RAM (I have one in mine)?
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
    Nubus/ISA/VLB/MCA/EISA cards of all types
    Boxed apps and games for the above systems
    Analog video capture cards/software and complete systems

  8. #28
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    Quote Originally Posted by dJOS View Post
    I did reach out to the maker of that board and asked if I could use his schematic but he never replied unfortunately.
    Aw, foo. I was actually going to open a thread specifically about that thing and ask if anyone had the schematic for it to see if I could just possibly try cooking up something like that myself. Or, at least, just the additional RAM part. I'm planning to put a modded Gotek in my machine so I'm not sure I'm *that* bothered about having the IDE interface, in the near term. But I've been coming to the conclusion that I'm probably going to need more than 256k to experience at least a plurality of Tandy-specific video games.

    Maybe at some point I'll noodle over the lo-tech schematics and see if I can work it out. It certainly looks like you don't need a lot of glue to just hang an SRAM off of an ISA-ish bus and it shouldn't be too hard to lay that out. Famous last words.

  9. #29
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    Quote Originally Posted by blackepyon View Post
    I don't know if the EX/HX support Upper memory blocks or not
    Really stupid idea: According to the EX technical manual the blocks at D0000 and E0000 are open, and it looks like that's where the IBM PCjr mapped its cartridge slots. I wonder if you could map 128k in there, load it with the contents of a PCjr cartridge, and fire it off.

    Granted that's mostly a theoretical question given the amount of PCjr cartridge software that actually exists...

  10. #30
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