Octek PVGA1C 16 bit card in 8 bit XT slot - almost works, jumpers?

[Chr$]

Hello.

This Octek PVGA1C 16 bit card works - almost - in an XT clone 8 bit slot (but not all slots physically had room for it due to m/b chips located where the 16 bit extension hangs down). Using the factory BIOS that the computer came with (A PC/XT TURBO clone of some kind) I get a 'SYSTEM Error # 04' reported on the screen at boot, which I believe indicates a graphic card RAM error. Pressing any key results in it booting as normal. Using other common clone XT BIOSes I get no error and it merrily boots all the way as normal.

I can't find any info online about this card and the jumpers labelled JW1, JP1, JP2 (not populated), JP3 and JW2 (hard wired as connected) all in the upper left corner and JP4 and JP5 in the lower right corner. Changing the position or removing the jumpers that have pins has no effect in combination with the PC/XT TURBO BIOS and always results in 'SYSTEM Error # 04' at boot.


I mean, it's not the end of the world, I could just use a BIOS that is less fussy with it, but I thought I would ask here to see if anyone has encountered this card or may have a link to what its jumpers do and whether it may be possible to use this card with my original BIOS.

Thanks.

 

[Chuck(G)]

How did you set your motherboard switches 5 and 6?

 

[Chr$]

Good point. I can't remember, will have to check tomorrow.

 

[Chr$]

I had 5=ON and 6=OFF so changed it to ON/ON. Switches an absolute pig to get to on this board, I had to remove all 4 drives. Anyway, it didn't change anything, it still gives me the same error. I suppose I should check the switch is working but that can be for another day as it would take some time to expose the m/b.

 

[Chuck(G)]

Do you think that the error message comes from the VGA BIOS or from the motherboard BIOS? If the system comes up, it should be a simple matter to search for the message text in both. If it's the VGA BIOS, then it's likely there's an issue there. Are you running an 8088 or a V20 CPU? Sometimes the VGA BIOS vendors will slip in a 80286/186 instruction without intending to. If the error goes away with a V20 CPU, you have your answer.

 

[Chr$]

It comes from the motherboard BIOS (attached). It's running a standard 8088, but I do have a V20 I could try, and that's fairly easy to access. The board in question is my (DTC) Display Telecommunications Corporation "Megaboard". Just preparing the system for sale as I've decided to save space by just keeping amy original IBM XT.

 

[Chuck(G)]

If the switches are set correctly, the motherboard BIOS shouldn't even be looking at the video memory. Very puzzling.