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

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    Originally posted by Eudimorphodon View Post
    Yeah. I have this bad feeling I might have screwed this up even if I had breadboarded the design, because there's a fair chance it's an error I introduced while running the tracks on the board. (It took me several false starts to come up with a board that didn't have a million awkward vias in it, so I was trying to follow some advice about paying attention to the physical layout of the chips instead of the schematic view when choosing how to route signals. In the course of that I switched the order of the data lines through the buffer a couple times, both directionally and end-to-end, I might have just lost track or flipped the direction hi-low in my head at some point.)

    At least it should be an easy fix for rev 2, if that ever happens.
    Yeah, that's something I found when designing my boards too. If it makes more sense for routing to rearrange the gates on a logic IC or a '688 comparitor, etc, from what's in the schematics, then that's what you end up doing, but you gotta make sure you update the schematic at the same time, otherwise you'll tie yourself in knots quickly. It helps having multiple monitors for that, so you can have the schematics and board layout side by side.
    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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      In other news, I installed Check-It 3.0 onto a disk image, and according to its memory mapping function it sees 128k of high memory in addition to the expected "624k" of base RAM.

      memmap.jpg

      I've set it to continuously run the rigorous RAM test for a while just for laughs. (It passed the quick test fine.) The only thing separating this from the brain-dead 74x00 one-chip version is a little more gate delay in the decoding (and the one address line that'd be a little delayed compared to the others) so I don't expect any issues, but we'll see.

      Also just for the sake of testing I've plugged my modem card into one of the pass-through bus slots, and I can confirm that the spacing is right. Check-it sees the serial port integrated into the card so I'll take it as read pass-through works.

      modem.jpg

      Looking at how I laid things out if I end up offering the rest of my proto run to intrepid DIY-ers I might just recommend skipping the buffer and soldering wires across the socket. (As you said it's not great, but boards like the Lo-tech RAM card get away with it, I guess.) Unfortunately the MEMW trace that goes to the memory chips goes *through* the land on the buffer socket on its way to the bus connector, so to sever it free would take two jumpers/trace cuts to free up the pin and bridge the two subsystems to their different bus points. I suppose another workaround would be to just bend up pin 1 of the '245 and run a flying wire to MEMR; I could anchor it to the backside of the down-facing tandy bus connector. Guess that's going to be my test strategy.
      My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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        Hah. Earlier in the thread we brought up the "mempdrvr.exe" file on the oldschool.org Tandy 1000 archive that can create a RAM disk on the (rare?) 512k version of the official Plus memory board. Apparently it's compatible with the UMBs on my card.

        ramdisk.jpg

        It initialized and seemed to work fine. (I could copy files to it, etc, and they survived when I ran memory-intensive programs in base RAM. Amazing it's only 921 byte binary.) Now I'm curious again what the memory mapping for the original card was like when it was installed in an HX. That omnibus collection of Tandy jumper settings said it had different settings depending on whether it was installed in an HX or an EX; obviously the E000 page is out, did you only get 64k in an HX or did it take the C000 page?
        My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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          And it's confirmed, bad direction signal. Cobbled up this solderless jumper arrangement to test and it works

          20190719_174836.jpg

          Interesting side observation: I used the jumper for the E000 page to construct this, and the RAMdisk software refused to initialize with only 64k.
          My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

          Comment


            This is progress! Congrats!
            Still gonna build up that board when it arrives though. I'm curious to see it.
            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


              If nothing else it might be interesting to run a few benchmarks, since you have access to the DMA equipped board, and see if it makes any difference. Topbench scores my EX a bit slower than the SX in its database, I'm curious if that's normal.
              My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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                Yeah, I'll give that a go.
                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


                  Originally posted by Eudimorphodon View Post
                  If nothing else it might be interesting to run a few benchmarks, since you have access to the DMA equipped board, and see if it makes any difference. Topbench scores my EX a bit slower than the SX in its database, I'm curious if that's normal.
                  Topbench scores my SX a point slower than the SX in its database

                  Comment


                    Originally posted by GrandPoobah View Post
                    Topbench scores my SX a point slower than the SX in its database
                    Looking at the screenshot of my scores I do wonder if this is a case of being right on top of the rounding mark.
                    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                    Comment


                      Originally posted by blackepyon View Post
                      Yeah, I'll give that a go.
                      I have a few ideas of hacks that might be interesting to try if you get bored with it, too. (in particular I've been wondering if it would be legit to map the calendar chip at D000 along with the lower UMB, in order to incorporate the calendar into a Flash-less board. I think you could test that by bending up the CE lines for the DS1315 and hacking some wires to the enable jumper.)
                      My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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                        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

                        Comment


                          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 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


                            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.

                            Comment


                              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 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


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

                                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.
                                [ATTACH=CONFIG]53974[/ATTACH]
                                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.
                                My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

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