First post, by quicknick
I recently acquired some XT-class parts, and since I haven't touched this kind of stuff for more than 20 years... Well, I have some questions.
There is this DTK PIM-640K motherboard, couldn't find much about it but it seems it is quite similar to other DTK models, so jumper/switch settings are not a problem. It had 640KB of RAM, but one 4164 chip was missing so I removed the whole 3rd bank until I can find a spare.
But I'm left wondering... Why so many (empty) ROM sockets? What could go in those? ROM BASIC? Is XT-IDE a possibility? Are there more "modern" BIOSes that add features that were lacking in the original XT?
The board works, started at first attempt with one of my 16-bit VGA cards that also work on 8-bit slots, but hangs with a "Disk not setting ok" error. Haven't tried to go further, because I don't have any XT keyboard and I don't know yet if any of my multi-IO cards will work on 8-bit slots (only have 16-bit cards). To solve the keyboard part I guess that I'll have to build the AT2XT keyboard converter described on Vintage Computer Forum, but if anyone has other ideas... please shout.
The second board is a Samsung Electronics XT board, also with 640KB RAM - it has onboard serial, parallel ports, floppy controller, real-time clock and video (Paradise PVC4, CGA-compatible from what I've read), all of which can be individually enabled/disabled with jumpers. Things are quite straightforward with this one: also POSTed at first attempt, but after a few test it halts with a "Keyboard Error, press F1 to continue". 😁 I had to use the same VGA card because I don't have any CGA monitor around (and cannot get one because of space)... And this brings another question - what can I use to convert CGA/EGA to VGA? Ebay seems flooded with converters, do I choose one at random or does anyone use a specific model and can recommend it to me?
Regarding both boards, do you think they will support 1.44MB floppies?
Last, there is this 8-bit video card. Couldn't find much info about it. The main chip is Compaq branded, 104495-001. The ROM is an OKI M3864, which has some peculiarities (two Chip Select lines) so my TL866 can't read it. There are four 4416 RAM chips. There is a D-Sub 9 pin connector, a RCA one (composite?) and a 3-pin header (light pen?). Couldn't test it, as I said there's no monitor, and I'm yet to source a cable to connect what I suspect is Composite out to my TV.
The text on board:
ASSEMBLY NO. 000525
DIAGRAM NO. 000526
VDU CONTROLLER, GA3
BOARD NO. 00527-001