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

  • alank2
    replied
    Originally posted by rkrenicki View Post
    So, I missed a single ground connection. The board works correctly now. I published the gerbers on my Git, along with a BOM. Now that I know that these are good, I am going to start working out the schematic into KiCAD.
    https://github.com/rkrenicki/Tandy1000-DMA-Upgrade
    Do you have any of these boards available?

    Leave a comment:


  • blackepyon
    replied
    Originally posted by bladamson View Post
    I think the DMA controller on the older Tandies was just a convenient way to do dram refresh since the video circuit couldn't do it on the expansion ram. The fact that is enabled DMA with expansion cards was just kind of an extra feature. I don't think it's really needed on that class of machine. I mean, the main reason to have it would be to make an 8-bit SoundBlaster work, but I don't think anything that will run on that class of machine will support more than AdLib anyway for the most part.
    Yeah, my main goal here was to get a viable RAM expansion going for the EX/HX, since they're pretty limited without it.

    Everything else is just window dressing at this point, but I'm quite pleased with the other ideas that have branched off of this thread. A couple years ago, there wasn't anything available, and now everybody is making their own all-in-one cards!

    Leave a comment:


  • Eudimorphodon
    replied
    So, also kind of off topic except for how it applies to making "Combo" expansion cards that include XT-CF implementations...

    I just finished throwing together a second example of my new GAL-based card (so for the first time I'm running the same thing in both the EX and the HX), and when throwing it into the 1000 SUX for testing I decided just for the heck of it to try re-testing a random sample of a big batch of Compact Flash cards which had failed Disktest's mediatest with my previous boards. To cut to the chase, no; the same cards fail with the GAL implementation as did with the discrete decoding. (TL;DR, under 256MB cards that ID as "STI" are generally fine, anything that says "Unigen" or "Smart" is garbage. Unfortunately for me that includes all my 512MB and 2GB cards.)

    Not really a surprise or anything, but, man. It's kind of disappointing just how hit and miss CF card compatibility is. Makes me hope nothing changes with those cheap PATA->SD card adapters to ruin their so-far perfect 8-bit compatibility.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by Eudimorphodon View Post
    It might be fun to make a version that uses surface-mount RAM since, you know, why have 1MB of useless EMS RAM when you could have 4MB?
    Nothing like a case of the "might as well's."

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by bladamson View Post
    It is indeed extremely cool. I will probably try to get a bare board from you sometime, when you have spares. ;P
    Heh. I need to figure out if I need to make more that fix the trace error, I guess. I have four more boards from the prototype run, for just my use I can hack the mistakes on one of them to take care of my needs, but... you know how crud like this is never actually finished anyway. It might be fun to make a version that uses surface-mount RAM since, you know, why have 1MB of useless EMS RAM when you could have 4MB?

    Leave a comment:


  • bladamson
    replied
    Originally posted by Eudimorphodon View Post
    I am actually pretty proud of this board, all things considered.
    It is indeed extremely cool. I will probably try to get a bare board from you sometime, when you have spares. ;P

    Leave a comment:


  • Eudimorphodon
    replied
    Originally posted by bladamson View Post
    Ohhhhh but now you will have to write a fancy multi-tasker that will swap to EMS. And restores graphics modes, too. I wanna see all the SSI games running at the same time, on an HX. :3
    Heh. I'll get right on it after I figure out why the Tandy 4-color graphics driver for Windows 2.11 won't let me run with DOS loaded into a UMB.

    I am actually pretty proud of this board, all things considered. It was the first thing I've ever made with programmable logic and it works better than I could have dared hope; it's set up hosting a network card in the populated passthrough connector in the ol' 1000 SUX and the hardware seems like it's rock solid. (It was an exciting few hours the first night fixing the bugs in the GAL formulas and figuring out the boneheaded mistake I made with the EMS decoder, but with those issues ironed out it's been great.)

    Am still waiting for some Amtel (current production) GALs to show up so I can make sure they work as well as the old recycled pulls that're in there now. I've heard of people having mixed luck with those ATFxvx chips.

    Leave a comment:


  • bladamson
    replied
    Originally posted by Eudimorphodon View Post
    EMS memory *is* pretty pointless in an EX/HX for anything but shock value, but I did want to see if it could be done and I had enough I/O left over on the GALs to do it. Fun stuff.
    Ohhhhh but now you will have to write a fancy multi-tasker that will swap to EMS. And restores graphics modes, too. I wanna see all the SSI games running at the same time, on an HX. :3

    Leave a comment:


  • dJOS
    replied
    Nice work!

    Leave a comment:


  • Eudimorphodon
    replied
    I guess since this thread is about DMA again this is kind of off-topic, but for laughs here's the thing I've been working on the last couple months. (Been talking about it in some other threads here and there relating to specific functionality/software for testing, etc.)

    Tandy_EMS_Card.jpg

    For lack of a better name it's the "Handy Dandy Ram-O-Matic". Basically I stuck everything from my old boards onto one along with two more RAM chips and an EMS memory page-flipper and replaced all the discrete decode logic with a couple GALs. Been testing it for about a week now and outside of a boo-boo with the EMS logic that needed a hack on the back it seems like it's all good. Just verified the one bug I could find with the last prototypes, an issue with DOS Kermit serial file transfers, seems to be resolved.

    EMS memory *is* pretty pointless in an EX/HX for anything but shock value, but I did want to see if it could be done and I had enough I/O left over on the GALs to do it. Fun stuff.

    Leave a comment:


  • dJOS
    replied
    Classic! It doesn’t take much to screw up sometimes. I recall missing some really minor details when I was reverse engineering the SmartWatch modules. So frustrating at the time!

    Leave a comment:


  • rkrenicki
    replied
    So, I missed a single ground connection. The board works correctly now. I published the gerbers on my Git, along with a BOM. Now that I know that these are good, I am going to start working out the schematic into KiCAD.

    https://github.com/rkrenicki/Tandy1000-DMA-Upgrade

    Leave a comment:


  • rkrenicki
    replied
    I picked up a Northgate Omnikey 102, so I have a functioning keyboard at this point.

    The RAM portion passes every test I have thrown at it. Disk access works perfectly fine, as long as I boot from an XTIDE... but I cannot get this system to boot from floppy disk while this card is installed. I may have made an error on the DMA portion (specifically DMA 2), or there may be an issue with my particular computer. I asked to borrow the original card again so I can test it in my machine and probe out a couple of traces that were unclear on my scans (obscured by silkscreen).

    I should have that board either tomorrow or early next week, and I will have some further updates. I am very eager to get the gerbers out to the community, but I want to ensure that they are perfect before I do so.

    Leave a comment:


  • blackepyon
    replied
    Originally posted by rkrenicki View Post
    The first draft boards have arrived. My 1000A and the logic chips needed to build this board will arrive tomorrow, so I will have initial testing done sometime tomorrow afternoon.
    [ATTACH=CONFIG]60536[/ATTACH]
    Glad you were able to pick that up. My business has been shorthanded since this whole coronavirus thing started, and haven't had time to work on any of my hobby projects.

    Leave a comment:


  • dJOS
    replied
    Originally posted by Eudimorphodon View Post
    ImageDisk does indeed tell you to drop dead. (I don't have a Tandy *with* DMA to compare, but without testfdc fails with the claim of "no floppy interrupt".)
    I cant even run IMD from floppy disk on any of my DMA equipped machines, including a K6 machine - during loading it thinks the disks have bad sectors even when they are newly created Virtual images (HFE or IMG). But, if I copy the files to HDD and then run it, it's perfect. I only use 1.17 as the archive on his site for 1.18 is missing the IMD.COM file. I tried emailing him about it but got no response.

    Leave a comment:

Working...
X