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

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    If someone could fit 640K RAM, two UARTs, IDE controller, and a smartwatch on one card that would be perfect.

    As soon as my dual riser comes in from DJOS I will try out running the MEM/IDE/SERIAL/VGA cards all at once, no reason to believe it won't work, and with the ability to 3d print a card box bump to allow for the 4th card it will be easy to make it all fit and work well together.

  2. #172

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    Quote Originally Posted by RetroGaming Roundup View Post
    If someone could fit 640K RAM, two UARTs, IDE controller, and a smartwatch on one card that would be perfect.

    As soon as my dual riser comes in from DJOS I will try out running the MEM/IDE/SERIAL/VGA cards all at once, no reason to believe it won't work, and with the ability to 3d print a card box bump to allow for the 4th card it will be easy to make it all fit and work well together.
    I've often thought about doing something like that .... but finding time is an issue.

    That reminds me, I have a few orders to build tonight when I get home from work.
    My Retro Collection:
    CBM: C64, Amiga 500 x2, 600 & 1200
    Mac's: SE, LC630 & Beige G3
    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

  3. #173
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    Quote Originally Posted by RetroGaming Roundup View Post
    If someone could fit 640K RAM, two UARTs, IDE controller, and a smartwatch on one card that would be perfect.

    As soon as my dual riser comes in from DJOS I will try out running the MEM/IDE/SERIAL/VGA cards all at once, no reason to believe it won't work, and with the ability to 3d print a card box bump to allow for the 4th card it will be easy to make it all fit and work well together.
    I can understand wanting to fit VGA into it, given how hard CGA/EGA (TTL) monitors are to find (at a decent price anyways), but I'm not certain whether or not it will recognize an external video BIOS. Worth a shot though. I'm fortunate enough to have two TTL monitors.

    Creating an all in one card is definitely possible, if one combined as many of the discrete chips as possible into one or more FPGAs, but that's a bit beyond my skill at the moment. Eeguru was attempting something like that (see page 1).
    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.

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    The XT VGA card works fine in the HX, and of course supports CGA/EGA/VGA, if I want to run TGA I can use my CGA to VGA converter with the on board video and use the same VGA monitor. http://www.vcfed.org/forum/showthrea...452#post578452

  5. #175
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    I used to have an 8-bit CGA/EGA/VGA card at one point. But yeah, what I wasn't sure of was whether it would recognize the card's BIOS and send signals to it in place of the onboard TGA. Good to see that it does that.
    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.

  6. #176
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    Quote Originally Posted by blackepyon View Post
    Doesn't need to be pretty. Just drop the KiCad project folder onto Mediafire or somewhere and drop me a link. I can prototype it on a breadboard on my end to make sure that there's not some hidden difference we might have missed between the EX and HX that might be interfering (I DOUBT that would be the case, but just to make sure).
    Would you have any interest in fooling with one of my PCBs? I have nine spares, I can't imagine it'd cost much to drop one in a padded envelope and send it your way unless there's some ridiculous custom charge that's likely to kick in. PM me if you're interested at all.

    As an aside, my order of smartwatches came in, and I imagine you won't have any trouble guessing how loud the forehead slap was when I opened it and found I'd accidentally ordered SMT packages instead of DIP. (I would have sworn that "DIP" appeared in the product description when I ordered it, but apparently not, and now I'm clear on how "+5" and "-5" in the part number denote DIP verses SMT for those things. Whee.) That probably explains why it was only $13 for five of them. I have a harebrained plan to try adapting one to a DIP footprint using copper wire jumpers bent around a notched piece of plastic acting as an insulator/ interposer.

  7. #177
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    I sent you a PM with my address.

    Quote Originally Posted by Eudimorphodon View Post
    ...I imagine you won't have any trouble guessing how loud the forehead slap was when I opened it and found I'd accidentally ordered SMT packages instead of DIP.
    Could be worse. I paid $23 CDN for just ONE DS1315-5+-ND from Digi-Key with my last order (which is in the DIP footprint). Haven't had time to play with it yet. $13 (USD, I assume) for 5 isn't too bad. I don't see any reason why you wouldn't be able to use prototyping wire to connect to the DIP pads, just to use up what you got. Just wouldn't want to send out any kits with those :P
    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.

  8. #178
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    It lives!

    chkdisk.jpg

    I gave in and ordered some new RAM chips from Digikey, which arrived last night. Yanked out all the jumpers, repopulated the board... and it still didn't work. Based on a gnawing hunch I pulled out the 74HCT245 and jumpered the data lines across the socket, and that time it fired right up to "Memory Size = 640k". I've run several things like Topbench:

    topbench.jpg

    That didn't fit in 256k and it's been seemingly working fine. I also banged up a brain-dead little BASIC program to poke values into the UMBs at D000 and E000 and it looks like they work as well:

    rampoke.jpg

    (After poking values into the UMBs I went peeking around the other memory pages and it looks like the remapping circuitry I came up with to get full utilization out of the RAM chip is doing its job, I didn't see any duplication of page contents.)

    Obviously I need to do some formal RAM tests and find something to exercise the UMBs, but so far so good. I think I've found the issue with the buffer; I need to cut a trace and solder in a bodge wire to be sure, but I think I got the "direction" signal for the '245 flipped. I'm not sure if it was a "deliberate" error from misreading the datasheet or if it's just something I accidentally missed at some point when I was shuffling the circuit board layout. (I did flip the A->B direction through the buffer a couple times laying it out to try to get the layout as clean as possible.) It currently connects to MEMW, I think it needs to go to MEMR instead.

    So, yay, it works. I'm still not sure this exonerates the eBay'ed RAM chips, though, because I'm pretty sure I tried this configuration before. I'll try swapping one of them back in after I've gotten the buffer working.

    I guess now I get to see if it stays to one bodge or if it'll need more hacking for the calendar and flash to work. Could be worse!

  9. #179
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    I was thinking of the '245 direction as well, because that's the same mistake I made on my breadboard. That's one reason it helps to debug it on a breadboard first to make sure you didn't miss something silly:P

    Strictly speaking, it's not necessary to have the '245, but like bypass caps, the more you have installed on the bus, the nosier the bus is going to get.
    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.

  10. #180
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    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.

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