I have no experience with this sorta of thing and thus unlikely to be any help, but I do like to learn so I googled the manual and noticed under Primary Display one of the options is: Not Installed. Also under Video Rom Shadow one of the options is Absent. I’m curious what/how exactly can you tell …

The board has indeed no on board video (that's a different SBC, I have one of those too). What would be the most simple video card, from a low level programming perspective? Hercules? Where would I find detailed programming information?

Is it possible to fake the presence of a video card on the ISA bus? I would my BIOS to see a ISA video adapter (HGA/CGA/EGA/VGA) so it will boot form disk. My stuff will communicate using the on-board COM ports, so I can live without a screen. The system is a very compact PC/104 but it needs a ISA …

Hello, My IBM PS/2 model 30 (8086 cpu) has a 3.5" 720k floppy drive which doesn't read any disks. Since I have a spare 720k floppy drive which works fine, I'm fairly sure that the floppy disk/controller/rest of pc are ok. Googling brings up the following topics: - clean heads (ok, did that) - …

Hi SSTV, Thanks for the link, this seems to be my board indeed! 😀 I'll jumper it correctly and see what it does...

JP6: 1-2: 256KB cache but BIOS complains JP6: 2-3: 64KB cache but Norton SI 8.0 gives a CPU Speed of 14.5 (386DX33 reference is 35.9, 486DX33 should be around 71)

This mainboard is labelled "OPTI-486WB REV 1.1" The closest (by name) I found is this one: http://www.amoretro.de/2012/03/opti495-486wb-ver-1-2-opti-493_486-motherboard-isa.html But the layout is completely different. Here is a picture: opti-484wb_rev1_1.jpg There was no CPU plugged, I guess a 486 …

Problem solved :) The best hint was this schematic in the winbond W83C42 datasheet: schematic.png The MEGATRENDS MEGA-KB-H-WP uses the same configuration and a 7406 next to it. Both copper traces for keyboard clock and data seem to be damaged, probably close to where the cmos battery was. The …

On a 486 mainboard I removed a leaky battery which was close to the keyboard connector. I seems to work but the keyboard does not work. The visible traces are ok but I can't find any connection to the keyboard controller. The 40 pin dip ic of which I assume it's the keyboard controller is labelled …

Does anyone have a datasheet or the pinout of the UMC UM82C491?

I still need to verify that the system runs stable and the RAM is ok, any recommended tool for this task? x86memtest didn't start at all (does it still support '486s?) Just to be sure, did you try to run memtest from a floppy and not from an optical disk? Afaicr booting from CDROM drive wasn't …

The AM486-DX2-50 might not need a heatsink but the cpu is a 80486DX-50, so the external bus will also be clocked at 50MHz (assuming the AM486-DX2-50 is 50/25MHz). The DX-33 definitely runs without heatsink. I tried to find an official intel datasheet (no success at ark) for the cpu, but I only found …

I've assembled a 486 pc, the cpu is a A80486DX-50 which probably needs a heat sink as it gets hot (= too warm to touch) quite fast. The plastic remains of a heat sink frame which attached the heat sink to the cpu are still there but broken beyond repair. I do have sticky heat sink foil to glue them …