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

Display Telecommunications Corporation "Megaboard".

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

    Display Telecommunications Corporation "Megaboard".

    Ok, have been exploring this early-ish clone board lately, here is what I have found:

    dtcmegaboard.jpg

    This is a Display Telecommunications Corporation "Megaboard". I don't know if it was always called that, or if they referred to it differently when part of a complete OEM system. It is not labeled as such.

    The DTC "Megaboard" is an early ~1983 IBM XT clone motherboard. Note this is not the same "DTC" that produced hard disk controller. Also do not confuse with "DTK".

    It was the first product of Display Telecommunications Corp. It was sold to OEMs and individuals as bare boards, kits, or assembled. It was used by hobbyists, experimenters and high-tech handypersons.

    There is an Infoworld article comparing it to other boards here:
    https://books.google.com/books?id=Bw...ard%22&f=false

    One ad lists:
    Display Telecommunications Corporation
    4100 Sprint Valley Rd, #400
    Dallas Tx 75234
    Bare board $99
    Socketed: $249.95
    Assembled $599.95

    DTC did sell cases and other parts for it.

    After clipping a shorted -12v tantalum capacitor, the board works great. Going by the chip dates, this specific board was manufactured in 1984.

    The ROMs contains a bootleg of the IBM 5160 11/08/82 BIOS with BASIC. From my research, it normally should have come with its own "megabios". Also from what I have read, supposedly the manual gave instruction how to copy the IBM ROM in to it, which some considered inappropriate.

    This board uses the same power supply interface as the PC/XT/AT. A standard AT supply works fine with it.

    The board is physically larger than an XT board. It will not fit in an XT or Baby AT case. The Keyboard plug does not line up and the board needs extra space for its reset switch. Still, it is mostly an XT clone and uses the 5160 ISA spacing.

    The board itself feels a little flimsy. All chips are socketed. On the one hand, socketed chips can be a bit less reliable, but on the other hand, could be easier to fix. I haven't looked up all of the part numbers, but It uses only basic 74LS chips to interface the main chips. (No PAL programming needed?)

    An odd implementation on this board, it has little metal divider shields between the main sections. While that was common on some earlier computers, I don't believe I have seen that on other IBM PC clone boards.

    Over all, this is a "no frills" motherboard, but it does have some developer-friendly aspects.

    Most visibly, it has perfboard area where one can their own custom circuitry. It features a reset switch next to the keyboard port.

    This board supposedly "features" slot 8 support identical to the IBM XT. Although, what was that ever used for? The board also has a card-edge connector that seems to extend the ISA slots.

    Jumpers permit ROMs to be configured in a variety of ways.

    By cutting/soldering jumper wires, the board can be configured to use either 16k, 64k, or 256k, RAM chips. This board contains a full 640k, although the Infoworld article suggests it would be limited to 256k.

    This board has also been maxed out with an NEC V20 and a math co-processor.

    Booting it, and throwing software at it, it seems perfectly IBM PC XT compatible. It passes all the diagnostics I have thrown at it. It works fine with VGA, XT keyboards, and an 8-bit 1.44mb floppy controller. Of course, remember this has an IBM BIOS in it.

    The only real issue with this motherboard is that it does not physically fit a standard XT case.

    Any rate, I think this in an interesting addition to my collection of early PC clone and parts.

    #2
    It's nice. Just get out the hacksaw. I have a rather largish Wang case I'd sell you cheap. You can go to town making a mess of that.

    Comment


      #3
      I didn't realize copying the IBM Basic ROMS was so common, this XT clone board I have
      also came with a copy of IBM Basic.

      DSCF0089.jpgDSCF0090.jpg

      Comment


        #4
        Growing up, our first computer was a DTC Megaboard clone. In fact, this machine is still in my parents' attic, so someday I will attempt to restore it.

        We had the OEM case which fit the board nicely. It had an oval-shaped cutout for the keyboard and reset switch (similar to PC 5150), and the lid was hinged so it opened up rather than sliding off. The front bezel was designed to look like an IBM only it had horizontal decorative lines instead of the vertical ones on the IBM. It had a rear power switch, and a black "Fortron"-branded power supply. I'm fairly certain it was all bought from DTC that way. I don't have any pics of it, as it's 1000 miles away.

        We had the "MegaBIOS" with it when we got it, however it was replaced at some point down the road with an ERSO BIOS probably due to some hardware compatibility issue (HD floppy drive, video card, maybe?), and unfortunately the original MegaBIOS chip was set aside and is probably gone forever now. I have a clear memory of the POST test booting up with the message "TESTING MEMORY /" (with a / \ flashing back and forth).

        I still have the original OEM manual and documentation for it. It goes into great detail about the theory of operation (logic diagrams, scope readings, etc) and also has the listing for the infamous "IBM MEMORY to INTEL HEX CONVERTER" BASIC program that allegedly lets you copy IBM BIOS ROMs (have never tried it) in order to "facilitate patching".

        Here's a few pics of some of the pages from the book:

        mb_cover.jpgmb_prod.jpgmb_pic.jpgmb_dip.jpgmb_basic_hexcov1.jpgmb_basic_hexcov2.jpg

        There doesn't seem to be a lot of info out there about the company beyond what you posted. I assume they probably stayed mostly a mail-order clone company, and just couldn't afford the R&D to stay competitive and eventually folded up. If anyone has any more story about what they did after this, I'd be really curious too.

        FK

        Comment


          #5
          Update - I managed to get the case out of storage and snapped some photos. The hard drive is of course non-functional, and those floppies need servicing but that original PSU started right up with good voltages on all rails. Interestingly the company, Fortron (not to be confused with Fortran or Voltron) is still in the power business today.

          The switched, standard AC outlets on the back were a nice feature so you could plug in a non-IBM monitor and I think we plugged in our printer too (before the days when we knew we should have a surge suppressor strip).

          I'm really interested to find an image of the original "MEGA-BIOS" bios chip, just to make it all complete. If anyone has that actual chip, would love to get a dump of it for archival purposes.

          FK
          Attached Files
          Last edited by frankiekat; August 24, 2021, 06:16 AM. Reason: added link to Fortron

          Comment


            #6
            There's something awry with the PM's. I got you PM's frankiekat and see a sentence or so in the notification email. When I go to the forum to read them they just show as blank (although yesterday I was able to read one of them). The one you sent with those pics shows the pics but no text. The text must be there somewhere. I can confirm that my case appears identical to yours. PSU is branded differently but also looks like it might be the same.

            Hmmm, just looked again the the PM's are no longer blank. Will reply now.
            http:\\www.QXL.WIN
            I'm Chris. I have a small collection of old IBM compatibles and a getting-rather-large collection of Sinclair QL related hardware and software items. Always on the look out for QL stuff if anyone has anything.

            Comment


              #7
              Originally posted by Chr$ View Post
              There's something awry with the PM's. I got you PM's frankiekat and see a sentence or so in the notification email. When I go to the forum to read them they just show as blank (although yesterday I was able to read one of them). The one you sent with those pics shows the pics but no text. The text must be there somewhere.
              That is a known ongoing issue that has been occurring since the hosting software (vBulletin) was upgraded at the VCF in April.
              Discussed in a few threads within the 'Vintage Computer Forum Support' section.
              Appears to be related to PM's with still-under-moderation members.

              Comment

              Working...
              X