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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
    Dang it, that's a good idea, and it would give me an excuse to put different silkscreen doodles on every card. Maybe for the next round.

    The gerbers passed the pre-manufacturing sniff test so they're on the way to the presses now. I'm both excited and thrilled with dread that something isn't going to be right. The usual.



    That's the main reason why I'm not sure it's worth adding the DMA controller, because an 8-bit Soundblaster is one of a *very* short list of things I can think of that would even use DMA on an XT class machine... and most of those things that could use it really kind of need a faster machine anyway. I mean, it'd be useful if you needed to run an old school XT disk controller, but if you have XTIDE built in instead then that reason *and* the improved floppy performance justification both kind of go out the window. (Although I guess the latter might break a few demos, possibly?)

    A far out thing that occurred to me is I think those old hand scanners that used 8-bit ISA cards needed DMA. I had one back in the day and I have to admit I'd find it amusing to play with one again. But I also remember it not running that well on the 286-12 I had it connected to, so just like any software that needs a Soundblaster I suspect it'd be a tough row to hoe for the Tandy to make any use of it.
    I've been thinking about that as well. DMA 0 is out of the question, since as has already been established, the newer SRAM doesn't need that refresh pulse, and the onboard RAM is being refreshed by Big Blue anyways. So really, it's just those "insane builds" with the riser expansions that could really take advantage for that rare card that actually needs it. I wouldn't mind trying my SoundBLASTER 2.0 Pro in 8-bit mode just to see if it can run it.

    Another thing one needs to consider for these "insane builds" is the limited number of IRQs the 1000 EX/HX have available. As I see it, only IRQ 2,3,4 are available on the expansion header, since everything "needed" is already built onto the motherboard. At least one of those is going to be taken by the serial card for your mouse, then if you add a NIC and sound card, IF they support those IRQs, you're pretty much full unless you want to run the risk of conflicts. The parallel port on my I/O card seems to work without an assigned IRQ (at least in send mode for the blinkenlights circuit I cobbled together), though I'm not sure serial would if you're using it to run a mouse.
    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 dJOS View Post
      Adrian has posted an update here:

      LOL! Everybody seems to wire up that '245 wrong the first time.
      (I'm not blameless there either )
      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 blackepyon View Post
        LOL! Everybody seems to wire up that '245 wrong the first time.
        (I'm not blameless there either )
        Yeah, guilty as charged here.

        I wonder if I should offer my flawed boards as some sort of door prize, since they only take a single wire to fix.
        My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

        Comment


          Hey, putting a 245 with the A side and B side flipped is nothing compared to the time I designed a board with the entire IO bus flipped side to side.. >.>

          Comment


            Originally posted by rkrenicki View Post
            Hey, putting a 245 with the A side and B side flipped is nothing compared to the time I designed a board with the entire IO bus flipped side to side.. >.>
            lol my first ISA adapter design was mirrored because I read the wrong diagram in the technical reference manual while designing it.
            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

            Comment


              Yeah, the PLUS expansion bus is more or less compatible with the XT (ISA) bus, but if you miss the fact that the A and B sides are flipped... You're gonna have a bad time!
              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 blackepyon View Post
                Yeah, the PLUS expansion bus is more or less compatible with the XT (ISA) bus, but if you miss the fact that the A and B sides are flipped... You're gonna have a bad time!
                I almost did manage to swap them when I was making my first card; the EX tech manual has diagrams on page 6 and page 9, and the two sides are swapped on the latter one, which I was referencing a lot because it's the one that translates any differences between standard ISA signal names and Tandy's names. (I can only assume the page 9 one was lifted straight from the conventionally-slotted 1000's tech reference.) I growled a lot when I realized my mistake and had to reconnect all the PCB routes, but I guess I at least caught *that* before I sent it off to the board mill.
                My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs Also: Blogspot

                Comment


                  Originally posted by Eudimorphodon View Post
                  I almost did manage to swap them when I was making my first card; the EX tech manual has diagrams on page 6 and page 9, and the two sides are swapped on the latter one, which I was referencing a lot because it's the one that translates any differences between standard ISA signal names and Tandy's names. (I can only assume the page 9 one was lifted straight from the conventionally-slotted 1000's tech reference.) I growled a lot when I realized my mistake and had to reconnect all the PCB routes, but I guess I at least caught *that* before I sent it off to the board mill.
                  Yep, that's the one that got me. Luckilly no damage was done - my EX just refused to boot.
                  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

                  Comment


                    Originally posted by dJOS View Post
                    Yep, that's the one that got me. Luckilly no damage was done - my EX just refused to boot.
                    I'm surprised you didn't fry the buffer on your card, with the +12v and -12v pins sitting opposite D0 and D2. The 5v pins won't kill anything immediately, but poking around with my multimeter the one time, my probe slipped and I accidentally fried the bus buffer on the motherboard in this manner. Fortunately, replacing that buffer chip fixed everything, but having that chip buggered prevented anything else on the data bus from working.
                    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 blackepyon View Post
                      I'm surprised you didn't fry the buffer on your card, with the +12v and -12v pins sitting opposite D0 and D2. The 5v pins won't kill anything immediately, but poking around with my multimeter the one time, my probe slipped and I accidentally fried the bus buffer on the motherboard in this manner. Fortunately, replacing that buffer chip fixed everything, but having that chip buggered prevented anything else on the data bus from working.
                      I was surprised too, but my CF-IDE card lived ... somehow. I saw the black screen plus no beep and powered off immediately.
                      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

                      Comment


                        Positive pressure on the inside of the enclosure.

                        Keeps the magic blue smoke in the chips. :3
                        -- Lee

                        If you get super-bored, try muh crappy Odysee channel: Old Computer Fun!

                        Looking For: QBus SCSI Controller, Type 4 HDC for Tandy II/12/16/6000, Mac IIci drive sled, PC-era Tandy stuff, Old Unix Stuff, Serial Terminals (HP and DG in particular)

                        Comment


                          20191106_223443016_iOS.jpg

                          My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

                          But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.

                          Comment


                            So, regarding the original intent of this post, I have a T512CLK-A1 here that I still intend to finish reverse engineering for it's DMA logic, which is entirely TTL.
                            IMG_20191107_063039644.jpg

                            I think we're all satisfied with the 00/32 RAM logic at this point, and people are building their own cards based on that, but once I finish up my current project, is there interest in having DMA function as well for "insane" EX/HX builds or is DMA just a curiosity for you guys? The RAM portion of the T512CLK is inconsequential at this point, and we've no need for DMA-0 since we're using static RAM, so it's basically down to whether or not you want the extra floppy performance and to run a sound card, scanner card, or something-whatever that can actually take advantage of DMA.

                            And then with the other DMA schematics (Sergey's 8088, the IBM 5150 technical reference manual, etc), we should be able to come up with a useful DMA circuit in case somebody wants to populate that section of the board.
                            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 rkrenicki View Post
                              [ATTACH=CONFIG]57177[/ATTACH]

                              My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

                              But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.
                              Looks nice, but you've got the external connectors on the wrong side of the board. :P This only matters if you intend to have anything on top of it.

                              By the way, what are you guys using for UART controllers? I've got an ISA multi-I/O card that I'm using for now, but I should probably work the RS232 into another card at some point to get rid of that annoying PLUS to ISA cable arrangement.
                              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 rkrenicki View Post
                                [ATTACH=CONFIG]57177[/ATTACH]

                                My first prototype of my 3-in-1 board arrived yesterday, and I quickly assembled one. It turns out that the footprint for my CF card slot was completely wrong for the part, so I did not assemble the XT-IDE portion of the board. I also apparently put the PLUS connector 2mm too far to the left, shifting the whole board to the right, so I needed to trim the board slightly to make it fit... but hey, that is what prototypes are for.

                                But, in the meantime, the SRAM and RS232 portions of the board seem to work well, and I am currently working on optimizing the layout to be a little less of a jumble.
                                Great work!

                                Comment

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