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Thread: Questions about WDM286 -WDM20 motherboard

  1. #1
    Join Date
    Jun 2013
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    Default Questions about WDM286 -WDM20 motherboard

    Hi guys, after successfully finding a 286 motherboard that can be enabled to use XT keyboards by jumper, to use on my ibm portable system now i have some questions.

    The motherboard in question is a WD286-WDM20:
    Here are all the jumpers lucky this guy have this nice web page:
    http://stason.org/TULARC/pc/motherbo...286-WDM20.html

    The motherboard seems very interesting to me have a lot of functionality build in including a video port chip paradise select-able between cga ega mda and ega 200 lines.
    So i selected the disable jumper and installed the original cga video card from the ibm portable and works nice.
    Also the motherboard have ps/2 mouse x2 serial ports and parallel port, its a fast 286-12mhz have 4 isa slots and 4 simm sockets.
    Installed X4 1 megabyte simms 30 pin on the sockets.

    The first problem is that to use this i don't have the header from the onboard video port and the manual don't includes a pinout. description if someone can supply it ?.

    Next problem is the video when i turn on the computer i get a video mismatch error and the display is CGA 40 column by default, added a "MODE CO80" to my autoexec to fix this, but the error always shows up and on the bios i selected CGA40 but cannot get rid of the error, maybe someone nows how to fix this ?.

    Another issue is for some reason the computer runs great run all kind of games and memory tests and get ok.
    When power the computer up for first time and is cold, pass the memory test on the bios ok.
    The problem is that after using it like an hour or more if i reboot or power off and on get a memory error on the bios.
    The chips in the simms are very hot i don't see any jumpers for memory speed on the motherboard maybe the memory is runing to fast and is overheating ?.

    It's a silly question but i like to run an MDA + CGA cards on the computer so if i like to run something on hercules mode i don't have to open the computer to change video cards, the issue is that (tried x2 different HERCULES clone cards) the computer always defaults to the hercules video output no matter if the cga card is in slot 0 and the hercules in slot 4, when i start after the bios my autoexec i inserted a "MODE CO80" statment, so it goes to CGA then.
    But could love to be able to see the bios on the embedded screen (CGA card) i'm not sure if this is possible?.

    Thanks!.

  2. #2

    Default

    Here's what I know about that board:

    1) I have the video cable/header but I'd have to examine it to discover what you want to know about it. The only fact I'm sure of (right now) is that it's a 10 pin header with a ribbon going to a DB 9 connector and the red stripe must go towards the rear of the board.

    2) The onboard video adapter can be disabled but it requires a combination of six jumpers:

    W13 OUT
    W18 2-3 for MDA, 1-2 for RGB, EGA, or VGA
    W23 Out
    W24 1-2 IN
    Unmarked jumper next to C106 and R101 (on right side of board when viewed from front) IN

    The last jumper is located on the extreme right side of the board (when viewed from the front) approximately 3 inches in front of the five-position dip switch that controls the video mode OUT

    3) That board only supports two displays when one of them is the onboard EGA. The other can be either CGA or MDA.

    You'll notice that W18 and that last unnamed jumper are not referenced in the link you posted to Stason.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  3. #3
    Join Date
    Jun 2013
    Location
    Montevideo, Uruguay
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    Default

    Quote Originally Posted by Stone View Post
    Here's what I know about that board:

    1) I have the video cable/header but I'd have to examine it to discover what you want to know about it. The only fact I'm sure of (right now) is that it's a 10 pin header with a ribbon going to a DB 9 connector and the red stripe must go towards the rear of the board.

    2) The onboard video adapter can be disabled but it requires a combination of six jumpers:

    W13 OUT
    W18 2-3 for MDA, 1-2 for RGB, EGA, or VGA
    W23 Out
    W24 1-2 IN
    Unmarked jumper next to C106 and R101 (on right side of board when viewed from front) IN

    The last jumper is located on the extreme right side of the board (when viewed from the front) approximately 3 inches in front of the five-position dip switch that controls the video mode OUT

    3) That board only supports two displays when one of them is the onboard EGA. The other can be either CGA or MDA.

    You'll notice that W18 and that last unnamed jumper are not referenced in the link you posted to Stason.
    Thanks for the reply i was missing the W18 jumper, set it up and the machine stopped nagging about the bad video adapter option.
    Also now if i insert the hercules + cga card together the computer will default to the CGA card ok .

    It could be cool to get the header pinout to use the onboard video is a shame the manual don't have it.

  4. #4

    Default

    Quote Originally Posted by soviet9922 View Post
    It could be cool to get the header pinout to use the onboard video is a shame the manual don't have it.
    IIRC, it's a straight ribbon cable from the header to the DB 9. If I had to guess I'd put the red stripe in the first position and leave the tenth position out of the DB 9. If you don't get it first I'll try to ohm it out when I can get to it.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  5. #5

    Default

    I just located it and it's not flat!

    The conductors are all separated and redirected to their prescribed positions. It's difficult to remove where it's located so I may or may not be able to reach it soon, if at all. I'll give it a go when I'm feeling more nimble. Also, the twisted array of conductors has a thick, spiral coil wrapped around it. Maybe it's a filter -- I forget what these are called.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  6. #6
    Join Date
    Jun 2013
    Location
    Montevideo, Uruguay
    Posts
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    Default

    Quote Originally Posted by Stone View Post
    I just located it and it's not flat!

    The conductors are all separated and redirected to their prescribed positions. It's difficult to remove where it's located so I may or may not be able to reach it soon, if at all. I'll give it a go when I'm feeling more nimble. Also, the twisted array of conductors has a thick, spiral coil wrapped around it. Maybe it's a filter -- I forget what these are called.
    Don't look very easy to check out at all sure is a ferrite core.

  7. #7

    Default

    You nailed it! It's a ferrite core.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  8. #8
    Join Date
    Jun 2013
    Location
    Montevideo, Uruguay
    Posts
    130

    Default

    Quote Originally Posted by Stone View Post
    You nailed it! It's a ferrite core.
    looking at the video header on the motherboard using the continuty tester i can see theres a single ground pin.
    it should not be to hard to get the correct pinout using a simple trial and error sheme.

  9. #9
    Join Date
    Jun 2013
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    Montevideo, Uruguay
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    Default

    i have now another bizarre issue, the motherboard came with 4 triple height 30 pinn simm's they are 256 k each.
    So they give me 640k + 384 shadow (thats what the bios say).
    The motherboard runs fine using this and i can install drdos 6 fine.

    Now if i replace them for some bigger 1 meg simms x4 sets (i have tried multiple memory sets that run fine in others machines), everthing seems ok i can run 20 times checkit 3 and pass all memory tests run games and programs ok using dos 6.22 but if i try to run drdos 6 installer i got a memory parity error instantly.
    Im not sure if my ram is bad incompatilbe or theres something different on drdos 6 ?.

  10. #10

    Default

    I remap that 384K and use it as a Ramdrive on mine.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

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