RayeR wrote on 2023-11-02, 12:41:

I already tried both PCI and ISA VGA carda but none works, video still goes from onboard VGA. According to M592 manual there's no such jumper and I cannot find any jumper that is not described in manual that would do it.

I see. Then I have another suggestion - BIOS editing. See if there's a hidden BIOS-menu option for selecting of which videocard to be initialized first (PCI, AGP or integrated). If there's such a thing, set it according to your needs and unhide it. For Award BIOS you can use suitable version of MODBIN (or MODBIN6 for newer Award BIOS core), for AMI - AMIBCP.

There's AMI BIOS. I have an idea that if I remove VGA BIOS module from system BIOS then it should give a chance for ext. VGA...

Of course, you can remove the entire VGA BIOS module, but better off first try with something less intrusive/destructive.

ok, i'll have a look with amibcp 1st. In the past I used modbin in some cases for award but didn't revealed any interesting hidded settings in my case...

I play with AMIBCP 7.6 and the BIOS. There was some hidden SETUP options but none relevant to onboard VGA.
But it's strange that I cannot find VGA BIOS module inside. There's one PCI ROM - some NCR SCSI. There was also some INT10h module but it's not VGA BIOS. Even if I deleted it from image and flashed modded BIOS the onboard VGA is still working and nothing changed. So it seems to be harder that I though. But I have no strong motivation to mess with such crappy MB so I leave it as is. Just curious how it works...

UPDATE:
wow, I cannot see ROM chip on these PCI VGA cards https://www.vgamuseum.info/index.php/cpu/item/390-sis-6215
So does it mean that the chip itself contains the VGA BIOS in ROM or FlashROM?

This is odd. I'm digging these days in some Award BIOSes potentially compatible with a "broken" (due to wrong BIOS flash) slot1 mobo with AGP slot and there is "Init Display First" option in the menus (with "Onboard" selection disabled, which can be enabled if needed) in all of them. I cant't remember for sure right now, but I think in AMI BIOSes this option is with similar name.

There is VGA BIOS module in my Elpina BA E-VO's (PCChips M571 3.2A) BIOS and I've successfully saved it to file with NSSI tool using the option to dump VGA BIOS which is in use.

Here's BIOS module list in AMIBCP. I explored all and none of them is VGA BIOS.

Here're two pictures from my M571-colone's BIOS-dump.

Obviously the VGA BIOS module is not named VGA-something. Use NSSI to save it to file it as I already wrote. Then you can search and compare this part in full motherboard's BIOS.

OK, I can't find menu-item to manage which video adapter to be initialized in this particular PCChips AMI BIOS, but I'm sure in other AMI BIOSes I've seen such an option.

As I mentioned, on my M751-clone mobo, when integrated video is excluseively activated by jumper and I insert some PCI videocard, the integrated auto-disables itself even with the jumper on its position for active integrated video. But with different BIOSes it's always a different mess.

Few points.
Are you sure the pci slots work?
Do they show in lspci / device manager?
Is the onboard a separate chip or integrated into the chipset?
Do you have a decent pic of the board?

Oh, I oversight the datasheet at bottom of VGA museum website. This explains a lot. My guess was right - the chip has internal 32kB ROM! I never seen this before... Of course it can be disabled and then the chip use external (flash)ROM via address and data bus. There is aslo strap feature that should allow completly disable the video chip.

From the datasheet:

D2 BIOS ROM decoding logic
0: Enable
1: Disable when MD18 is pulled up with resistor.
D1 Video subsystem enable/disable at power-on is
0: Controlled by System BIOS
1: Forced to disable when MD17 is pulled up with resistor

As manufacturer didn't added any jumper for this some wiring would be needed to add pull-up on MD17...

It's probably already there as a transistor which the bios is supposed to switch off when it finds another card

I made some better photo of my M592

Do you see the JP6 "jumper" (bridge) that is soldered to its position? There's no info about it in the manual. If this mobo was mine, I'd try changing its position by soldering a three pin jumper-header on its place.

Yes, I oversight this. Sure, no problem to solder pin header instead and try what it does 😀

Hm, flipping the jumper didn't help to run ext. VGA but internal VGA got scrambled screen. When I pulled jumper out I got just blank screen on internal VGA (monitor detected 720x350@70Hz but blank), ext. VGA no signal at all. So the jumper is somehow VGA related but not that I wanted. It had a reason to be hard-soldered.

I also tried add pull-up at pin MD17, 18. Either one disabled int. VGA but ext. VGA still doesn't boot up.
MD17 pull up - POST stops at code 2Ah (sooner), ext. PCI VGA no signal, ISA VGA out of range (94Hz)
MD18 pull up - POST stops at code 80h (later), ext. PCI VGA no signal, ISA VGA no signal
both pull ups - POST stops at code 80h (later), ext. PCI VGA no signal, ISA VGA out of range (97Hz)

After boot with onboard VGA both PCI VGAs are visible on the bus:

1PCI device #3 found at bus: 0, dev: 9, func: 0
2Vendor ID: 104Ch (Texas Instruments)
3Device ID: 3D07h, Revision ID: 1, Class: 03h (display adapter)
4Sub-Class: 00h (VGA controller)
5IRQ: 0, INTA, Cache line size: 0 Bytes, Latency: 64, max 48us, Status: 0280h
6BAR: EFFC0000h, EF000000h, EE800000h, 00000000h, 00000000h, 00000000h
7ROM base: EFFB0000h, Cardbus CISptr: 00000000h, Subs.VID: 1048h, Subs.ID: 0A32h
8CMD: IntDis-,FB2B-,SERREn-,WCC-,PER-,VGAPS-,MemWIEn-,SCE-,BusMa-,MemSEn-,IOSEn-
9
10PCI device #11 found at bus: 0, dev: 11, func: 0
11Vendor ID: 1039h (SIS)
12Device ID: 0204h, Revision ID: 33, Class: 03h (display adapter)
13Sub-Class: 00h (VGA controller)
14IRQ: 0, none, Cache line size: 0 Bytes, Latency: 0, max 0us, Status: 0200h
15BAR: FF400008h, EFFF0000h, 0000EC81h, 00000000h, 00000000h, 00000000h
16ROM base: EFFE8000h, Cardbus CISptr: 00000000h, Subs.VID: 1039h, Subs.ID: 0204h
17CMD: IntDis-,FB2B-,SERREn-,WCC-,PER-,VGAPS-,MemWIEn-,SCE-,BusMa-,MemSEn+,IOSEn+

Hmmm, that's really strange behaviour. What is this Texas Instruments videocard? Can you try with some known for its compatibility PCI videocard like for example S3 Trio or Virge/DX/GX?

Permedia2, I tried also with some cirrus logic, doesn't matter. One friend suggested me to lift up reset pin of onboard VGA while other pins should.left hiZ but I think that PCI bridge may still keep forwarding IO tranactions to onboard VGA instead of PCI slot so some BIOS hack maybe needed. I probably waste no more time with this crap...