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

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  • blackepyon
    replied
    Besides the RAM card, the RS-232 card would be the most useful, since you could connect an external modem to it, or a mouse.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by blackepyon View Post
    I've got the Tandy DMA/RAM card, my "PLUS" ISA-CF, and an ISA multi-I/O card on a PLUS to ISA ribbon that has to be folded upside down to make the entire stack fit.
    I guess the way I phrased the sentence was open to interpretation, what I meant was "what Plus card are you likely to find inside of a 256k EX/HX, if it has a card, that you might actually want to keep using?". My EX came with the modem, and I did happen to see an HX with just the serial card on eBay at one point.

    (The modem card in particular doesn't seem to be "rare", I kind of wonder if the 256K machine + modem combo was at some point positioned as a cheap terminal for getting into Compuserve or whatever.)

    Leave a comment:


  • blackepyon
    replied
    The "key" with ordering from Digi-Key is to keep a shopping cart open for your various projects, and wait until it totals over $100, that way you save by getting free shipping. Unless I need something right away, this is how I order. And when you order cheap components, like 74xx ICs, resistors (10k especially), diodes, etc, order more than you need, so you have spares for trying new ideas on a breadboard and prototyping future designs.

    If someone has just one card other than the RAM card it's probably either the useless modem card or the somewhat less-useless serial card.
    I've got the Tandy DMA/RAM card, my "PLUS" ISA-CF, and an ISA multi-I/O card on a PLUS to ISA ribbon that has to be folded upside down to make the entire stack fit.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by dJOS View Post
    Inventory mgmt is a total PITA, I suffer from that issue frequently.
    The other night I finally sat down determined to come up with a BOM for what it would cost quantity one to build up a bare boardset from Digi-Key and, quite frankly, it was pretty awful. The killers are of course the DUART and the DS1315, those together are more than $30. If you're willing to buy a batch of those from *slightly* sketchy sources you can make that part of the BOM come *way* down, like into the $4 ballpark for the same two chips... but then you're stuck asking yourself "sure, I can buy ten of these for less than the price of two from DigiKey, but will I actually ever use the dang things?!". I guess when I'm done building the prototype and, knock on wood, it checks out, I need to get off my rear and see if anyone is actually interested in buying the rest of the batch and in what form. (Bare boards, kits, completely assembled.)

    I kind of feel like I can't really go to Texelec until I actually have a "finished product", but... yeah, given they sell open-source things and my plan is to open up the GIT for my boards anyway if I can actually point to a satisfied customer or two maybe they'll talk to me.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by bladamson View Post
    I am trying to dream up a way to design my eventual printed board such that it has an ISA edge connector (for standard PC/XT systems), but also has a spot where an optional PLUS header can be soldered in. The ISA edge connector would have a perforated spot where it could be scored with a box knife and broken off on a bench edge, to make it fit in the EX/HX after the PLUS header is added. Although with as cheap as it is to produce boards in small quantities nowadays, I wonder if such a design would really be practical.
    The big gotchya, previously mentioned, is Plus boards *should* have their panel connectors on the opposite side from the components, unlike a standard ISA card, and that has some knock-on effects with regard to where it's kosher to place components relative to the back. Granted this doesn't matter if you're intending your board to be the only one in the machine. I've tried to make my boards technically possible to intermix with original Tandy cards, but I'll be the first to admit that it's unlikely anyone who *doesn't* have the Tandy RAM board to have a card that they'd want to reuse after upgrading their RAM.

    (If someone has just one card other than the RAM card it's probably either the useless modem card or the somewhat less-useless serial card. Technically you could mix either with my cards in a stack but it'd be pretty redundant. I do have a stock of the IDE-only daughterboard if someone did have the Plus serial card, or wanted to use the ISA riser for one they already bought.

    I wonder if anyone actually still has the "Digi-Mouse" Plus card and the matching mouse... and had it in a 256k machine.)

    Leave a comment:


  • dJOS
    replied
    Originally posted by bladamson View Post
    Yeah, I guess you really don't lose any board space with your riser, do you? I was coming at it from the angle of "gotta cram in as much as I can in a limited footprint", heh.

    Now if we could just find something that could be made into a functional and not-too-ugly PLUS bracket, we'd be all set eh? I've been known to make stuff like that with an improvised sheet-metal brake, a band saw, a drill press, and a set of taps, but I'd hate to do that for something that had to be made in quantities larger than one. D:
    You only lose the small amount of space needed for the PLUS connector which isn't much.

    I'm the same, I just mod ISA/PCI brackets.

    Leave a comment:


  • bladamson
    replied
    Originally posted by dJOS View Post
    That's easy, just include the Plus header and utilize my Riser Card which has the correct ISA spacing:

    https://www.tindie.com/products/cybe...sa-riser-card/
    Yeah, I guess you really don't lose any board space with your riser, do you? I was coming at it from the angle of "gotta cram in as much as I can in a limited footprint", heh.

    Now if we could just find something that could be made into a functional and not-too-ugly PLUS bracket, we'd be all set eh? I've been known to make stuff like that with an improvised sheet-metal brake, a band saw, a drill press, and a set of taps, but I'd hate to do that for something that had to be made in quantities larger than one. D:

    Leave a comment:


  • dJOS
    replied
    Originally posted by Eudimorphodon View Post
    Heh. Yeah, I mostly just imagine it'd be nice to just be able to unload a few to recover a bit of what I spent over the saga and keep them from going to waste; the idea of going all-in on making a side business of it fills me with a bit of existential dread. Inventory management for parts alone looks like a non-trivial challenge.
    I totally understand I was honestly shocked how many folks wanted my adapters (still am) that I made for myself out of necessity. It might be worth your while to team up with Texelec like James did so you don't have to worry about that side of things?

    Inventory mgmt is a total PITA, I suffer from that issue frequently.

    Leave a comment:


  • dJOS
    replied
    Originally posted by bladamson View Post
    I am trying to dream up a way to design my eventual printed board such that it has an ISA edge connector (for standard PC/XT systems), but also has a spot where an optional PLUS header can be soldered in. The ISA edge connector would have a perforated spot where it could be scored with a box knife and broken off on a bench edge, to make it fit in the EX/HX after the PLUS header is added. Although with as cheap as it is to produce boards in small quantities nowadays, I wonder if such a design would really be practical.
    That's easy, just include the Plus header and utilize my Riser Card which has the correct ISA spacing:

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

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by dJOS View Post
    I'm mainly messing about with my design for fun and learning - I'm not going to muddy the waters with another product. I'm happy to keep making my various simple adapters as long as folk want them - tbh I barely have the time to build those these days.
    Heh. Yeah, I mostly just imagine it'd be nice to just be able to unload a few to recover a bit of what I spent over the saga and keep them from going to waste; the idea of going all-in on making a side business of it fills me with a bit of existential dread. Inventory management for parts alone looks like a non-trivial challenge.

    Leave a comment:


  • bladamson
    replied
    Originally posted by Eudimorphodon View Post
    Hopefully there's enough people out there who need EX/HX expansion cards to absorb a few different designs, otherwise I'm going to have a bunch of nice PCB coasters lying around.
    I am trying to dream up a way to design my eventual printed board such that it has an ISA edge connector (for standard PC/XT systems), but also has a spot where an optional PLUS header can be soldered in. The ISA edge connector would have a perforated spot where it could be scored with a box knife and broken off on a bench edge, to make it fit in the EX/HX after the PLUS header is added. Although with as cheap as it is to produce boards in small quantities nowadays, I wonder if such a design would really be practical.

    Leave a comment:


  • bladamson
    replied
    Originally posted by rkrenicki View Post
    but what would one realistically install into an EX/HX that isn't already on this?
    Adlib, on a 90 degree ISA riser.

    Leave a comment:


  • dJOS
    replied
    Originally posted by Eudimorphodon View Post
    Hopefully there's enough people out there who need EX/HX expansion cards to absorb a few different designs, otherwise I'm going to have a bunch of nice PCB coasters lying around.
    I'm mainly messing about with my design for fun and learning - I'm not going to muddy the waters with another product. I'm happy to keep making my various simple adapters as long as folk want them - tbh I barely have the time to build those these days.

    Leave a comment:


  • Eudimorphodon
    replied
    I mostly use my EX for "general hackery" instead of gaming so I really appreciate having the clock. But it certainly wouldn't be necessary otherwise.

    (The reason why I want an ISA riser is for a network card so... I suppose I am aiming to scratch the more technical itch.)

    Hopefully there's enough people out there who need EX/HX expansion cards to absorb a few different designs, otherwise I'm going to have a bunch of nice PCB coasters lying around.

    Leave a comment:


  • dJOS
    replied
    Originally posted by rkrenicki View Post
    Huh, I had forgotten about the clock chip.. my HX already has one installed. I could go back and implement it into my next prototype, but honestly, it has very limited use for games of the era.

    I decided to go the Monotech XT-CF route on my next prototype, and use an IDE to CF adapter mounted "upside down" to get the CF interface. Those are cheaper than buying the sockets themselves new, and are less of a headache than surface mounting them with their 0.635mm pitch. I do not have any problems drag soldering 0.635 surface mount chips, but the CF sockets are always a pain for some reason.. It will require some modification of the backplate, but I still think it kills two birds with one stone by providing a backplate at the same time as fixing my CF socket issues.
    having an onboard clock is mostly useful for folks with XT-IDE as it helps manage the contents of the hard disk (from a human pov).

    Leave a comment:

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