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Thread: Rare Model II Boards

  1. #1

    Default Rare Model II Boards

    http://maben.homeip.net/static/s100/...%20catalog.pdf

    See Page 26

    I noticed a few Model II-6000 boards in the 1985 RS catalog that I have never seen. I was wondering if anyone here has ever seen or owned these boards.

    26-6501 Arcnet Board

    I've heard about and read a little of what I could find about the Arcnet board but I've never seen one.

    26-1223 ViaNet Board

    Never heard about a ViaNet board. Was it actually released?

    26-6503 16K Z80 Memory Board

    Interesting. I've seen the 32K and 64K Z80 boards of course, but never have seen a 16K board.


    Also of interest is the VIS Multiplexer on the same page. @kb2syd, I believe you own one of these. Does it use a special card or is it an RS-232 connection?


    Any other rare Model II boards that you may have run across in the past?

  2. #2

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    Quote Originally Posted by pski View Post
    Also of interest is the VIS Multiplexer on the same page. @kb2syd, I believe you own one of these. Does it use a special card or is it an RS-232 connection?
    I have a prototype. It plugs into Serial A on the model 16/6000. I found the configuration directions in the stash of manuals I found last week. Serial A from the MUX connects to Serial A on the model II. Serial B on the mux box is for a debugging terminal.

    Quote Originally Posted by pski View Post
    Any other rare Model II boards that you may have run across in the past?
    I have a 2 meg and 4 meg RAM board for the 6000 running Xenix. They don't work.

  3. #3

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    Quote Originally Posted by kb2syd View Post
    I have a 2 meg and 4 meg RAM board for the 6000 running Xenix. They don't work.
    Those require the MMU, don't they?

  4. #4

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    Quote Originally Posted by pski View Post
    Those require the MMU, don't they?
    There was no MMU in the computers that had them. They were used just for SWAP. The ones I have are from Sound Ideas here in NJ I believe.

  5. #5
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    The 16K Z80 board did exist, I have seen one in the flesh. I believe it increased the memory of a 64K Model II to 80K because there was a specific version (of function that required more than 64K) on Model II VisiCalc. No specifics as to what other uses the card had.

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  6. #6

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    Quote Originally Posted by TRS-Ian View Post
    The 16K Z80 board did exist, I have seen one in the flesh. I believe it increased the memory of a 64K Model II to 80K because there was a specific version (of function that required more than 64K) on Model II VisiCalc. No specifics as to what other uses the card had.

    Ian.
    Nice. Apparently it also allowed you to run TRSDOS-II (which required 80k) on a plain jane Model II. Model 16 didn't need it because TRSDOS-II can use the 68000 memory for the additional 16K. Model 12/16B/6000 didn't need it because the mainboard had the additional 16K.

  7. #7
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    Quote Originally Posted by pski View Post
    Nice. Apparently it also allowed you to run TRSDOS-II (which required 80k) on a plain jane Model II. Model 16 didn't need it because TRSDOS-II can use the 68000 memory for the additional 16K. Model 12/16B/6000 didn't need it because the mainboard had the additional 16K.
    Minor correction there: 16B/6000 may or may not have the 16K on the Z80 mainboard, again, since TRSDOS-II can use the memory on the 68K system (or the memory on a hard disk interface board). 12's came factory-equipped with the 16K extra; but if you add a card cage and a hard disk there could be conflicts between the 16K on the mainboard and the 16K on the HD interface. I had one of each of the 12/16B/6000, and neither the 16B nor the 6000 had the 16K populated on the mainboard(or, for that matter, any of the decoupling capacitors for the extra voltages the 16K requires). The 12 did.

    While the 16B and the 6000 are based on the 12's hardware, they are not strictly 'Model 12 systems with the 68K of two different versions' but are a bit different even on the Z80 mainboard. This is why that, even though we have a 6000 service manual scanned and online now, it would be very useful to have the 12 and 16B SM's to be able to compare the differences (and, on a related note, the 'new version' Model 4/Model 4 Gate Array' service manual would be useful, too, as there are some differences between the 4-GA and the 4P-GA, and so having the 4P/4P-GA SM, while very useful, isn't the full story).

    The Model 12 is the oldest of the three 'B-style' systems, and was sold in parallel with the II-based Model 16 for quite a while.
    --
    Bughlt: Sckmud
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  8. #8

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    Quote Originally Posted by lowen View Post
    12's came factory-equipped with the 16K extra; but if you add a card cage and a hard disk there could be conflicts between the 16K on the mainboard and the 16K on the HD interface. I had one of each of the 12/16B/6000, and neither the 16B nor the 6000 had the 16K populated on the mainboard(or, for that matter, any of the decoupling capacitors for the extra voltages the 16K requires). The 12 did.
    Thanks for the clarification. Do you know what the solution was when adding a card cage and HDA to a Model 12? Was it a RAM reduction on the mainboard? This may also have an impact on the Hans03 project.

  9. #9
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    Quote Originally Posted by pski View Post
    Thanks for the clarification. Do you know what the solution was when adding a card cage and HDA to a Model 12? Was it a RAM reduction on the mainboard? This may also have an impact on the Hans03 project.
    The Tandy-documented solution is to move the 16K on the HD interface to a different page, but disabling the 16K (jumper E38-E39) on the mainboard seems easier to me (EDIT: that is until I remembered just how 'fun' getting to the mainboard on these machines really is.... it's a lot easier to work on the expansion cards!). This is fully documented on page 12.2 (PDF page 44) in the 'notejump.pdf' file that is on most of the archives, and as Tandy_Notes_and_Jumpers.pdf in your own model2archive git repo.

    As to the 'more official' solution, I'm sure there was a card cage service manual at one point, but I've never seen one. I do remember seeing pages (I might have mailed to Kelly) from a service manual that included the HD interface board, but I don't recall if there was an install procedure. Tech Bulletin 12/16B:09 deals with the mainboard jumper differences between 12 and 16B, and includes the admonition to always check all Model 16B units in for repair to make sure that E38 - E39 are NOT jumpered (this jumper is the bank select for the 16K), and also includes the note that 16B does not have chips installed in U63-U70. And then there's page 44 in the notejump.pdf document.

    Further EDIT: Page 222 of the Tandy Jumpers document has the recommended HD interface board setup for installation in a Model 12 fully documented, and page 376 has the figure showing the jumpers as laid out on the HD interface board.
    Last edited by lowen; December 2nd, 2015 at 10:11 AM. Reason: Added pointer to jumper setup in the official Tandy jumpers document.
    --
    Bughlt: Sckmud
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  10. #10

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    This weekend, 2 of the rare boards mentioned in this post came into my shop. This is the first time I've seen these boards.

    26-6501 Arcnet Board
    IMG_2594.jpg

    26-6503 16K Z80 Memory Board
    IMG_2593.jpg

    These boards were discovered in four of five Model IIs that were actually pulled from a garbage dumpster 4 or 5 years ago outside of a recycling center in New Jersey. They must have been part of an Arcnet network at some institution in New Jersey in the early 1980s.

    IMG_2590.jpgIMG_2591.jpg

    The Arcnet board required the additional memory provided by the 26-6503 memory board which is why you will always find them together in the Model II. It's interesting to note that the memory board has accommodations for 2 additional banks of RAM. Also, in the Tandy Notes and Jumpers, this board is denoted as the 144K memory board. This leads me to think the additional banks can be populated with 64K each. Further investigation is warranted.

    I do have an Arcnet hub, so I have all the hardware to try to create an Arcnet network except for the coax cable. But, the software is going to be a challenge. Arcnet support was part of TRSDOS-II 4.3 and I have never come across a copy of this version. If you'd like to help get an Arcnet network running and you may have or know of TRSDOS-II 4.3 somewhere, please get in touch. There was also XENIX support for Arcnet in some software products, but apparently it was a hidden feature in XENIX. I will have to do more research.

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