VOGONS


First post, by retroegde

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I need help identifying this 8088 motherboard because it has a keyboard header that I need to properly wire-up. I also need to know what the switch settings are. I'll give details on this PC, which i think is OEM, if it helps with the board identification. The only identification I see on the board is PC-820804-35. Only marking on the case are referencing a model number of PC401. Case and motherboard both say made in Taiwan R.O.C. I had to cut the case to even get the motherboard out.

When I power it up it beeps once, attempts to read a floppy disk, and then the hard disk fires up and is loud as <bleep>. No video. The computer has two video cards and I've tried both without messing with any of the current settings.

I've been able to test the following items in my IBM 5150
- The monochrome card (DTK PII-134) works.
- The floppy controller card and drive (IBM labeled TM-100) also work.

It came with a loaded AST SixPakPlus which I couldn't get to work in the IBM 5150 but I may need to play around with it some more
The PC came with a Computer Memories 6426-S 21mb hard drive (wd1002s-wx2) controller which I can't test in my 5150 but I'm purchased a 5160 power supply so I'll be able to test soon.
The newer video card is a VEGA Video-7 (1986 with 1988 on BIOS). I haven't tried this out in the 5150 yet.
The BIOS is m5l2764K and I want to get the equipment to dump and read the contents.

I've checked Total Hardware (https://arvutimuuseum.ee/th99/) but not many motherboards without a keyboard connector.

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Reply 1 of 6, by Horun

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Very Simple quick search found nothing about the board. If the numbers started with 35- would think it a PcPartner...
Keyboards are actually simple: you have Ground, +5, Data and Clock. Using a DVM you should be able to easily find the Ground and +5. Most XT and AT kb connectors do not use the Pin 3 KB_Reset pin.
So only thing left is figure out which is Data and which is clock. Trial and error should work.

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Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 6, by retroegde

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UPDATE: I found that the VEGA Video-7 may not work anymore (more testing to come). What I did find was the switch block SW1 on the board is the same as the IBM 5150. (http://www.minuszerodegrees.net/5150/misc/515 … ch_settings.htm) I changed SW5 and SW6 to off and used the monochrome graphics card. I can now watch the machine boot. The boot screen looks like this video on youtube for a Copam PC-401/XT (https://www.youtube.com/watch?v=yORUpB9tC24) but it doesn't say Copam. The fact that Taiwan is on the case and motherboard show that it may be a Copam. Still need to figure out the keyboard header but maybe I can get by with trial and error and the photo from when I opened the case.

I booted a floppy to DOS and now I'm going to try that hard drive (fingers crossed).

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Reply 4 of 6, by Horun

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That is great ! Glad you got monitor and KB working. Yes a lot of XT clones used same switch settings but not always, good work !

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 5 of 6, by mkarcher

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I wonder why that board has two spots for the 8088 / 8087 combination. One socketed spot between the RAM and the ISA slots, and a sencond one between the ISA slots and the power connector (soldering points, no sockets here). The unpopulated position between the slots and the power connector is the "classic XT mainboard location", but why the heck would you put a second processor location anywhere else? Possibly the intention was to have a 8088 soldered in, and you could upgrade to a NEC V20 in the socket (yet the socket is also labelled 8088)?

Apart from that and the keyboard connector on the pin headers, the board looks like a typical (non-turbo) Taiwanese XT clone mainboard. Make sure to test the VEGA card (if it does work, after all) with the DIP switches set to "EGA/PGA/VGA", not "Color 80x25". "Color 80x25" enables the CGA support integrated as part of the XT BIOS instead of the VGA BIOS on that video card. XT-class computers are way less forgiving with the video switches than AT-class and later computers are.

Reply 6 of 6, by retroegde

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After some research the video card is a VEGA Video-7 Deluxe EGA. I got help with the switch settings from https://stason.org/TULARC/pc/graphics-cards/U … EGA-DELUXE.html.
I kept Switches 5 and 6 for SW1 setting on the motherboard to ON so the video card ROM handles the dirty work. Then I can change the switch options on the back of the card to swap between my 5151 and 5153. I with I had an EGA monitor to see the improvement in graphics. Maybe down the road.