Correct PCI video init procedure during POST \ VOGONS

Correct PCI video init procedure during POST

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First post, by Yftul

Posted on 2025-04-05, 19:37

Yftul Offline

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Hi, All.

I have the 486-vip-io2 486 PCI board and Creative Labs CT6950 PCI riva TNT2 PCI card.
When I using latest bios the card is not initialized properly, booting is ok, but no image displayed. If I using bios from the board with same chipset DFI
G486VPC, the video initialized ok(but this configuration is not usable due another io chip). Older cards, like S3 trio or virge works ok on both bioses(HW the same anyway).

I tried to disassemble both bioses and not found any significant differences between PCI devises initialization procedures. Can anybody point me, whatI have to see to add proper init for riva card in original bios?

Кто хочет ищет средства, кто не хочет - причины.

Reply 1 of 5, by mockingbird

Posted on 2025-05-22, 13:53

mockingbird Offline

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See this post here, maybe it'll be helpful.

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Reply 2 of 5, by Yftul

Posted on 2025-05-22, 15:23

Yftul Offline

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Thank you.
It seems that a hardware issue is being considered here, but my problem cannot be hardware-related, since everything either works or doesn't work on the same motherboard depending on the BIOS version.

Кто хочет ищет средства, кто не хочет - причины.

Reply 3 of 5, by mockingbird

Posted on 2025-05-22, 21:41

mockingbird Offline

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Yftul wrote on 2025-05-22, 15:23:

Thank you.
It seems that a hardware issue is being considered here, but my problem cannot be hardware-related, since everything either works or doesn't work on the same motherboard depending on the BIOS version.

From what I can remember, it's related to the initialization routines. I base this on a post I saw on this forum years ago with regard to Matrox cards... He created a fix for it, but I can't locate the post at the moment -- the one I linked to is the closest thing I found to it.

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Reply 4 of 5, by Yftul

Posted on 2025-05-27, 14:56

Yftul Offline

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Looks like I've identified at least one of the issues. When saving the BIOS dump "blindly", about 37 KB gets copied, but everything beyond 32 KB is filled with FF values. I'll look for the video BIOS copy routine — the problem likely lies there.

Кто хочет ищет средства, кто не хочет - причины.

Reply 5 of 5, by Yftul

Posted on 2025-05-30, 06:09

Yftul Offline

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The problem is definitely that the BIOS does not support VBIOS images larger than 32K. Attempts to fix it have been unsuccessful so far: everything works perfectly in the 86Box emulator, but not on real hardware. However, at least now I can enter the BIOS on my physical machine.

Кто хочет ищет средства, кто не хочет - причины.

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