Announcement

Collapse

Forum Rules and Etiquette

Our mission ...

This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Rule 1: Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Rule 2: Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Rule 3: Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


Rule 4: "PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Rule 5: Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

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

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • blackepyon
    replied
    Originally posted by Eudimorphodon View Post
    The... eccentricities, I'm running into are all part of the fun. I'm just getting amused at how the well of differences between these machines and regular old boring PCs doesn't seem to be showing any sign of bottoming out.
    Likewise.
    I find it interesting how Tandy managed to combine so many things to save space and costs. Such as mentioned above, how the EX/HX have the V-sync circuit coming out of the interrupt controller. The keyboard controller has pins controlling sound and floppy, and the parallel port controller manages some of the floppy controls as well. And the relationships change between each model.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by Eudimorphodon View Post
    Have you checked the schematic yet to see where that goes? Does it just go to the audio amplifier circuitry (via a crude mixer?) to act as a remote speaker for a card, or is it more sophisticated than that.
    That seems to be what it is. B8 goes to U25, a "14529." Google thinks it's a Ford window switch, so can't say exactly, but it's directly in front of the op-amp, and the 3-voice sound chip also feeds into it, so it's some kind of sound controller. Grab the technical reference manual from Oldskool if you don't already have it.

    The EX/HX have B8 not connected to anything, so you would't get the pass-through audio there.
    Last edited by blackepyon; November 14, 2019, 11:27 PM.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by blackepyon View Post
    They still had pin B8 (slot-8/card select) as an "audio in." I'm guessing that was for the modem card?
    Have you checked the schematic yet to see where that goes? Does it just go to the audio amplifier circuitry (via a crude mixer?) to act as a remote speaker for a card, or is it more sophisticated than that.

    Ironically the EX modem has a big 'ol speaker on it, so I'm kind of doubting it used it.

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by blackepyon View Post
    The great thing about the Tandy 1000 line, unlike the early IBM 515X series, is that pretty much everything you needed to function was already on board, and didn't cost you an arm and a leg.
    Oh, don't get me wrong here, I'm in no way ragging on the Tandy 1000. The... eccentricities, I'm running into are all part of the fun. I'm just getting amused at how the well of differences between these machines and regular old boring PCs doesn't seem to be showing any sign of bottoming out.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by Eudimorphodon View Post
    The SX was the first 1000 family machine to have the DMA controller integrated onto the motherboard. I'm guessing Tandy concluded that since they didn't need any "extra" lines to implement the DMA control bus anymore they might as well eliminate their proprietary mapping of those pins.
    They still had pin B8 (slot-8/card select) as an "audio in." I'm guessing that was for the modem card?

    Leave a comment:


  • dJOS
    replied
    Originally posted by Eudimorphodon View Post
    Well, I've been having some fun with in-depth testing. So far I think my hardware is actually just fine, but it's kind of amazing some of the machine-specific quirks I've run into.

    Does anyone who's keeping an eye on this thread happen to use an Ethernet card in their EX/HX using whatever kind of adapter you've made, bought, or otherwise magic-ed into existence? I'd be curious to hear what you're using and what hardware resources you've assigned it.
    I'm using a WiModem 232 for all external comms - works great for my needs.

    Leave a comment:


  • blackepyon
    replied
    The great thing about the Tandy 1000 line, unlike the early IBM 515X series, is that pretty much everything you needed to function was already on board, and didn't cost you an arm and a leg.

    I contemplated, briefly, whether or not it would be possible to gang another 8259 to add more IRQs to the EX/HX. I think it IS possible, but it would require either cutting traces, or socketing a special daughterboard, making a custom psudo "16"-bit expansion bus for the extra IRQs, etc.... Not really worth it, IMO, but could be fun as a thought experiment.

    Leave a comment:


  • Eudimorphodon
    replied
    The SX was the first 1000 family machine to have the DMA controller integrated onto the motherboard. I'm guessing Tandy concluded that since they didn't need any "extra" lines to implement the DMA control bus anymore they might as well eliminate their proprietary mapping of those pins.

    Thanks to some help in the other thread I was able to solve the particular issue that was vexing me, IE, not actually being able to use IRQ2 for the Realtek 8019AS ethernet card despite the hardware supporting the mapping. As discussed on that thread IRQ2 is itself kind of an interesting edge case for usability; it's fine with XT-vintage hardware and software, but because the AT architecture pirates IRQ2 and attaches the same pin to IRQ9 on the second interrupt controller apparently some software that otherwise runs on an XT, like the "native" packet driver for the Realtek card, won't run with the card on IRQ2 because it makes AT-centric assumptions. Technically it's a stupid bug in the driver that could probably be easily fixed, but I wonder if there are other examples of that sort of thing lurking out there just waiting to bite.

    (The workaround here was leveraging the card's NE2000 compatibility and using an 8-bit compatible NE2000 driver that allows manually specifying the I/O and IRQ settings accurately.)

    Another thing I've started noticing is there really does seem to be a non-trivial amount of DOS software from the early 90's and later that doesn't like 8088 CPUs but will run on V-20s. So far I've left the 8088 CPU in my HX test rig, and I can confirm that in addition to the current version of Cutemouse being a problem there seems to be an issue with DOS Kermit; a weird, funky issue that's going to force me to break out my second eBay V-20 to absolutely confirm it. Fun stuff!

    Leave a comment:


  • Agent Orange
    replied
    Originally posted by blackepyon View Post
    That's interesting. It looks like the SX had IRQ 2-7 present on the expansion bus, but had jumpers to disable the interupt on the onboard video, FDC, and printer port. Presumably to allow add-on cards in their places. Question is whether or not the onboard devices work without the interrupts?
    Back then you were limited to the smaller 8-bit cards because of the 1000's short chassis. I never used a serial port on my SX as I went with the bus mouse. IRQ's were never much of a problem because you were pretty much constrained as far a peripheral or add-on card size. The printer was easy as it has its own dedicated parallel edge connector. Some outfit, I think it was 'Leprechaun', used to advertise an expansion case in 80 Micro for about $700. I don't think it was a very big seller. Since you were limited to 5 slots you had to do some planning. I had an EGA card, bus mouse, RTC, WDC, and of course - the modem. Also, there was a mono audio card that I occasionally swapped in and out with the modem. That's pretty much the way it is today, but the RTC is now piggybacked on the BIOS chip and the HD is a CF running off one of Hargle's first XT-IDE cards. One of the 5.25's has been replaced with a 3.5 and the EGA has given way to a garden variety 640 x 480 VGA. THe CPU is a V20 and there is a 80387 on-board as well. The very first mod to this box was to bump the RAM up to 640 KB. The original WD controller and ST-225 still function but are put away for safekeeping. My grand kids couldn't care less about this stuff but the latest crop of great grand sons show some promise.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by Agent Orange View Post
    ...Turns out the SX didn't require that mod as the IRQ's are selectable on the motherboard. (something to do with IRQ2 & IRQ5).
    That's interesting. It looks like the SX had IRQ 2-7 present on the expansion bus, but had jumpers to disable the interupt on the onboard video, FDC, and printer port. Presumably to allow add-on cards in their places. Question is whether or not the onboard devices work without the interrupts?

    Leave a comment:


  • Agent Orange
    replied
    Originally posted by Eudimorphodon View Post
    . . . which is what triggered the question about what slot resources people are actually successfully using in their Tandy 1000s.
    The second PC card that I ever bought for my 1000SX back in '87 or so, was a 300 baud dial-up modem - don't remember the brand, 'Harry Swartz' I guess, and the first was a bus mouse (still works). IIRC, it had some DIP switches and a slip of paper on how to set it up. It always worked and slow wasn't a problem because who could afford anything faster back then for home use? It was stunning to be able to connect to some board and actually send stuff back and forth. I had some job related experience with acoustic couplers back in the early 80's, but this was way better. I don't think IRQ's present much of problem with 1000's even with a HD. I still have a WD 8-bit MFM controller which has been modified for the early 1000 by altering the IRQ assignment. Somewhere, I still might have the write-up on how to do it, and it involves simply cutting a trace and soldering in a jumper. Got this 'fix' from tech who worked for WD and moonlighted at a RS store. Turns out the SX didn't require that mod as the IRQ's are selectable on the motherboard. (something to do with IRQ2 & IRQ5).

    Leave a comment:


  • Eudimorphodon
    replied
    You may have seen my other thread about getting an Ethernet card for my EX, which is what triggered the question about what slot resources people are actually successfully using in their Tandy 1000s. It's starting to feel like the limited IRQ selection might possibly a bigger strike against completely "gonzo" builds for these machines than no DMA might be. I do find myself wishing that IRQ7 at least came to the slot connector; it was pretty common practice back in the day to piggyback onto that and just accept you weren't going to be printing and whatever-else-ing at the same time.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by Eudimorphodon View Post
    Well, I've been having some fun with in-depth testing. So far I think my hardware is actually just fine, but it's kind of amazing some of the machine-specific quirks I've run into.

    Does anyone who's keeping an eye on this thread happen to use an Ethernet card in their EX/HX using whatever kind of adapter you've made, bought, or otherwise magic-ed into existence? I'd be curious to hear what you're using and what hardware resources you've assigned it.
    I think EEGuru was trying to get a custom built one going at some point (check the first page of this thread). There's plenty of hardware I/O availible, but only three IRQs to choose from, 2,3 & 4, as that's all that's been routed to the expansion header. IRQ 5 is used for the vertical refresh circuit (because reasons), and IRQ 7 is for the onboard parallel port, so they didn't bother routing those to the header. A few "unused" pins on the expansion header are instead used for DMA control functions to the MB from the DMA/RAM card that aren't normally available on an expansion bus, which is why I wanted to reverse-engineer that T512 card (my next project, once I verify that my PLUS-IDE board is working).
    Last edited by blackepyon; November 14, 2019, 06:19 AM.

    Leave a comment:


  • Eudimorphodon
    replied
    Well, I've been having some fun with in-depth testing. So far I think my hardware is actually just fine, but it's kind of amazing some of the machine-specific quirks I've run into.

    Does anyone who's keeping an eye on this thread happen to use an Ethernet card in their EX/HX using whatever kind of adapter you've made, bought, or otherwise magic-ed into existence? I'd be curious to hear what you're using and what hardware resources you've assigned it.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by bladamson View Post
    I have some ISA proto cards whose brackets have a break-out section (kinda like you see on electrical junction boxes) that's set up so you can break it out for different sizes of d-sub connector. It's a little ugly-looking, but something like that might be best? It's past my bedtime for now, but I'll try to remember to go up and take some pictures tomorrow evening and attach them.

    Barring that, I think if I was gonna cut very many with a dremel, I'd try to find someone with a CNC mill instead. =:3 Hmm although I guess if it didn't have to be exactly D-shaped, it could be done with only two plunge and cuts on a manual mill anyway.
    Knockouts would need a punch if you're getting them fabricated, which drives the cost up. Besides, knockouts are only really useful for those particular connectors.

    Leave a comment:

Working...
X