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8 bit mode on 16 bit video card for an XT clone

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First post, by AaronY

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Hi,

I've bought a new XT clone system, complete, just recently.
Unfortunately, the Monitor it came with doesn't work at the moment (I've opened it and the insides looks like it was buried in mud).

As a solution, it seems like I should be able to use a 16 bit VGA card in 8 bit mode.
With some research, it looks like I happen to already have to cards that should work.
They both work in a 16 bit slot, but I cannot get them to work in either of my two XT Clone systems.
(The other clone came in a 5155 case and has the IBM CGA card with AV out, so I know both do boot up.)

The two video cards in question are:
A Trident TVGA9000B & a Trident TVGA8900B.

The clone computers are:
a Laser xt/3 (I think, it came in the 5155 case) with a 10 mhz Fujisu 8086 processor
and a DTK PIM-TB10-Z with a 10 mhz Siemens 8088 processor.

As I understand, both of the video cards are ones that should work on XT computers and have jumper settings to change between 16 and 8 bit.

Is there something I'm missing?
I don't understand how nether card works on either system.
Any help would be appreciated
(before I need to start saving to buy something to get it to work)

Thanks

-Aaron

Reply 1 of 5, by jmarsh

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If they boot up with CGA they won't be configured to use a VGA card correctly.
There are probably switches on the motherboards to set the type of graphics adapter installed. For example google says the XT/3 needs DIP switches 5 and 6 both set to ON for VGA.

Reply 2 of 5, by AaronY

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I have tried that.
Both have two the switches to set the video modes.
I have tried all the settings, in case I was reading something wrong.
If it is set to anything other that extended, I get the no video beep code.
If I set it to extended, it sounds like it boots in, but I get no signal to the screen.

I have been testing these on a newer flat panel screen - I don't know if that will effect anything, as the cards work on this screen in 16 bit mode.

Reply 3 of 5, by Hoof

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Could be the vga bios uses 286 instructions. I have a hp paradise vga card that won’t boot in my ps/2 with stock 8086, but does with a NEC V30 (which has a number of 286 instructions). Maybe your cards came out when 8086/8088 pcs were no longer a viable market for vga cards, thus the bios was written for 286/386 pcs?

Reply 4 of 5, by AaronY

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I had wondered if there was some sort of compatibility with the card's bios.
I thought to check that with my 386 board (where one of the cards live), but the only 8bit slot has components in the way of the 16bit part so I can't fit in to try it.
If it is a bios thing, I wonder if it would be possible to update it to a compatible version.

A NEC V30 looks to be cheaper than any 8bit graphics cards that I could use... if it came to that.

Reply 5 of 5, by AaronY

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I found the manual for the 9000i on minus 0.
It says it is compatible, but make a note to check the appendix.

It says to check the system bios date:
"If your ROMBIOS shows a date earlier than October27, 1982, you will need to replace your system ROMBIOS to work with the adapter. Earlier versions of the ROMBIOS for computers manufactured in 1981 or 1982 do not support EGA or VGA graphics modes"

My bios has 1984, 1987 and '88 showing on the boot screen before the mem check...

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