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

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    #31
    Originally posted by Eudimorphodon View Post
    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...
    I don't see why not, since those cartridges are basically just ROMs in a slot, and the EX/HX can boot from ROMs. I was referring more to RAM and applications that specifically were written to take advantage of UMB, or how the existing blocks on the Tandy 1000 where the UMB section would be that are dedicated to ROM and video, are addressed or reshuffled if that area is used as RAM. That's one of the things I was hoping to test with my prototype, but I've since gotten sidetracked.
    My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

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      #32
      Originally posted by Eudimorphodon View Post
      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.
      I think the early Sierra games could run with 256K, but yeah, it's really limiting without that RAM expansion.

      Mainly, you need to figure out the addressing logic on that 688 for whatever memory section you need. That's what the jumper pins on the 1MB card set.
      My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

      Comment


        #33
        Originally posted by Unknown_K View Post
        How rare is the memory board for the 1000 desktop that gives you full RAM (I have one in mine)?
        If you're EX/HX didn't come with one, they're a bitch to find, as are any other PLUS cards. Fortunately, when my dad got his (the one that I have now), he got it with the memory expansion card.
        My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

        Comment


          #34
          Originally posted by blackepyon View Post
          If you're EX/HX didn't come with one, they're a bitch to find, as are any other PLUS cards. Fortunately, when my dad got his (the one that I have now), he got it with the memory expansion card.
          I meant the 1000A not the HX/EX.
          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

          Comment


            #35
            Originally posted by Unknown_K View Post
            I meant the 1000A not the HX/EX.
            You see them floating around now and then, but they're not too common. I've got a generic one with 512K that I was reverse engineering for the DMA controller (Tandy specific interface) that I was hoping to sell once I was finished with it. Good news though, is that because that machine actually has 8-bit ISA slots, Lo-Tech's 1MB RAM card is just the quick fix you need if you can get by without DMA, so that's what most people do.
            My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

            Comment


              #36
              Originally posted by blackepyon View Post
              I don't see why not, since those cartridges are basically just ROMs in a slot, and the EX/HX can boot from ROMs. I was referring more to RAM and applications that specifically were written to take advantage of UMB, or how the existing blocks on the Tandy 1000 where the UMB section would be that are dedicated to ROM and video, are addressed or reshuffled if that area is used as RAM. That's one of the things I was hoping to test with my prototype, but I've since gotten sidetracked.
              Yeah. Mostly what I was thinking there is if that 128k block in the Tandy EX/HX was really free as the tech manual seems to imply that might be a good place to map the extra 128k you'll have left over from a 512kx8 SRAM after you backfill up to 640k. (32 pin 512kx8s seem to be readily available in DIP form, so that's promising; I can kind of handle through-hole but been too much of a wimp to tackle surface mount yet.) If there's software that works on XTs that will let you take advantage of statically mapped UMBs then you should be able to use it there? The PCjr cartridge thing was just a random idea for a stupid pet trick you might be able to pull off with RAM mapped there.

              Most of my DOS knowledge is at least 20 years stale, I have a lot of catching up to do. Even if there's something as simple as a RAMDISK driver that would let you use a 128k UMB on an XT that could be useful for that old trick of copying command.com to it.
              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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                #37
                Originally posted by Eudimorphodon View Post
                Yeah. Mostly what I was thinking there is if that 128k block in the Tandy EX/HX was really free as the tech manual seems to imply that might be a good place to map the extra 128k you'll have left over from a 512kx8 SRAM after you backfill up to 640k. (32 pin 512kx8s seem to be readily available in DIP form, so that's promising; I can kind of handle through-hole but been too much of a wimp to tackle surface mount yet.) If there's software that works on XTs that will let you take advantage of statically mapped UMBs then you should be able to use it there? The PCjr cartridge thing was just a random idea for a stupid pet trick you might be able to pull off with RAM mapped there.

                Most of my DOS knowledge is at least 20 years stale, I have a lot of catching up to do. Even if there's something as simple as a RAMDISK driver that would let you use a 128k UMB on an XT that could be useful for that old trick of copying command.com to it.
                What I don't know about UMB is whether the system detects and manages that extra RAM, or if the software has to specifically look for it or already be configured with the addresses.
                My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

                Comment


                  #38
                  Originally posted by blackepyon View Post
                  What I don't know about UMB is whether the system detects and manages that extra RAM, or if the software has to specifically look for it or already be configured with the addresses.
                  So far as I'm aware no PC knows anything about UMBs? From what I recall you generally configure them either in hardware using an EMS 4.0-capable memory card or with the appropriate MMU-tickling software on 386 and later machines.

                  This look like a super useful thread:

                  http://www.vcfed.org/forum/showthrea...s-high-on-a-XT

                  Therein is a memory card design that looks like might be a predecessor to the lo-tech card using a 512k SRAM chip and showing the decode circuitry, and referencing drivers like USE!UMBS.SYS and DOSMAX.

                  UMBs aside, the Tandy manual seems to show the A0000 block is also free. I wonder if it would be kosher to map another 64k there contiguously with the rest of it and just throw out the 64k at B0000 for 704k. (Apparently the Tandy machines mirror the memory buffer used by video in low memory to the normal CGA location so mapping the whole 512k contiguously would be out.)

                  I'm starting to think at this point I need to order the SRAM chip and get a piece of protoboard so I can have them on the shelf mocking me. No, gotta hack FlashFloppy onto that GoTek first...
                  My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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                    #39
                    Originally posted by blackepyon View Post
                    I'm also working on an all-in-one PLUS CompactFlash storage card based on the XT-IDE/CF-IDE for the Tandy 1000 EX/HX.
                    I know I am pretty late to the party here, but I actually just finished designing one of these. It is basically a modification of the XT-CF-Lite V4.1 to use the PLUS bus instead. I just sent the design off for fabrication of some prototype boards earlier today.

                    I also sent you a PM about another matter.

                    Comment


                      #40
                      Originally posted by rkrenicki View Post
                      I know I am pretty late to the party here, but I actually just finished designing one of these. It is basically a modification of the XT-CF-Lite V4.1 to use the PLUS bus instead. I just sent the design off for fabrication of some prototype boards earlier today.
                      Sweet! The more, the merrier. Too few cards were made for this bus, despite how popular the EX/HX were. Do you have a good source for mounting brackets? My idea was to use a cutout of PCB soldered on at a right angle to keep costs down.

                      As per usual, everything draws attention away from my "hobby," but I'll have to redo my own design anyways since Altium's cloud-based Circuitmaker isn't designed for exporting to other formats (I've tried unsuccessfully to extract from the local files into something readable), which makes it harder to share with anybody not using the service.

                      I'm using Ki-Cad from now on. CircuitMaker is a really nice program (especially the auto-routing feature, which saves a lot of time in preliminary layout), but being cloud based is proving to be more trouble than it's worth for me.
                      My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

                      Comment


                        #41
                        Originally posted by rkrenicki View Post
                        I know I am pretty late to the party here, but I actually just finished designing one of these. It is basically a modification of the XT-CF-Lite V4.1 to use the PLUS bus instead. I just sent the design off for fabrication of some prototype boards earlier today.
                        Does your XT-CF Tandy board layout include a RAM expansion, or is it just the IDE circuitry?

                        I'm about finished with a Kicad layout for a brain-dead three chip RAM backfill board (sans DMA, of course) using a circuit I came up with that I suspect is pretty close to that RAM card for an original Tandy 1000 that was brought up a page or so ago. Currently dithering whether I want to send it off to a PCB mill as-is or indulge in a probably failed attempt given my level of experience to try to merge the memory circuit with an XT-CF on one grand board.
                        My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                        Comment


                          #42
                          It is nothing more than a XT-CF-Lite board adapted to fit into the PLUS slot. Memory was next on my "to-do" list, and I am open to trying to combine the designs to one board.
                          20190601_010705057_iOS.jpg

                          20190601_140030671_iOS.jpg

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                            #43
                            Some quick constructive criticism, if I may:

                            PLUS boards have the back panel connectors on the bottom side, and the bracket itself is mounted facing the bottom, so ideally you'd move the CF slot to the bottom side. Not an uncommon mistake, but you can only use two slots like this. If you're just doing this for yourself, it may not be an issue, and it's not something that everybody has to worry about. I notice because I've got all three slots on my HX populated, so precise alignment is critical in my case.

                            Otherwise, you've got the copyrights listed, and everything looks good!
                            My vintage systems: Tandy 1000 HX, Tandy 1000 RSX, Tandy 1100FD, Tandy 64K CoCo 2, Commodore VIC-20, Hyundai Super16TE (XT clone), 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, and is less likely to lead to a fatal accident.

                            Comment


                              #44
                              I blew my evening tonight trying to lay out a PCB that didn't look like it was routed by a monkey for my latest design iteration, which I might actually build up the courage to send to a PCB mill after I see if someone I know who should have some good advice will consent to look over it. Here's KiCad's 3D rendering:

                              Tandy-RAM-CF.jpg

                              This board has a 512k SRAM for backfilling to either 640k or 704k (there's a jumper just in case), 32k of flash at C8000, and a Dallas 1315 clock-calendar chip. My idea, which may be a terrible one, is to use stacking headers like used for Arduino, etc, shields to carry the Plus bus directly through instead of using the offset connectors like the original Plus RAM board. Then if this board works phase 2 is a board that has the CF support circuitry/header and a serial port on it. (And the board can be simpler because the flash memory is already taken care of, it'll only have port I/O devices.) Stacked together that would give me most of what I want in my EX, but if I also use a stacking header on that board it wouldn't foreclose sticking another layer on top.

                              That's the bad idea, anyway. There are probably a lot of things I haven't thought of.
                              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                              Comment


                                #45
                                Originally posted by blackepyon View Post
                                Some quick constructive criticism, if I may:

                                PLUS boards have the back panel connectors on the bottom side, and the bracket itself is mounted facing the bottom, so ideally you'd move the CF slot to the bottom side. Not an uncommon mistake, but you can only use two slots like this. If you're just doing this for yourself, it may not be an issue, and it's not something that everybody has to worry about. I notice because I've got all three slots on my HX populated, so precise alignment is critical in my case.

                                Otherwise, you've got the copyrights listed, and everything looks good!
                                Yep, I did not originally realize that, and flipping the board over will require essentially redesigning the entire layout which I have not yet done. This is essentially an off-the-shelf XT-CF-Lite mated to a PLUS-to-ISA adapter built onto one board.

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