VOGONS


First post, by Hamby

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I know you can stick a VGA card and a mono card in the same (ISA slot) computer.

But I was wondering if you could stick two separate VGA cards connected two separate monitors to, say, a Socket-7 motherboard with ISA/PCI/AGP slots?
How you'd tell the PC which display to talk to when... dunno.
DOS and Win95/95 almost certainly couldn't support it, but I wonder if a legacy Linux distro could? It would require a multitasking OS, I guess (hence Linux... maybe Desqview?)

I wouldn't even care if it was an ISA VGA card with an AGP VGA card... (though managing to get a CGA/EGA ISA card working with an AGP VGA would actually be useful, I think).

Reply 1 of 7, by weedeewee

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never tried it due to lack of cards, but you could get multiple matrox milleniums in the same computer. possibly even use the milleniums as secondary cards to some other brands primary if the drivers cooperate. just needed to have one card do the standard vga bios and the other cards were handled by the driver. probably only worked in windows, linux & perhaps os2.

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Reply 2 of 7, by waterbeesje

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Myth Pentium pro machine has a Matrox onboard and a separate and next to it. They are fine with eachother.

Also I've had some Pentium in the past which had two PCI cards but it tended to be random which card was primary. It was a mess that way :p

Some later computers may let you select in BIOS which card is primary, AGP or PCI (or igp if available)

Stuck at 10MHz...

Reply 3 of 7, by dionb

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Mono plus colour card in old systems worked because their BIOS occupied different addresses. All VGA cards occupy same BIOS address space. So only one can be primary, they can't work together at low level the same way. Specific drivers for OS could allow it, but that would require one driver written for both cards/chips, think Appian Jeronimo, 3Dfx Voodoo 5 or ATi Rage Fury Maxx (or some older, rarer things in Win3.x era, like Miro's dual S3 cards). Two unrelated cards would need at least Win2k in Windows world.

Linux has other possibilities, although I remember Xinerama (the X extension that offered it) as a collossal headache 20 years ago tbh.

Reply 4 of 7, by digistorm

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AGP+PCI works on my Slot-A motherboard with Win98 installed. You can choose which card you want to boot with in the BIOS and that is the card that DOS will use. Windows 98 supports both if you enable them. I don’t use it because my PCI card is too slow, I use it only for VESA modes that my AGP card doesn’t support 😉

Reply 5 of 7, by jakethompson1

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dionb wrote on 2021-08-01, 20:37:

Mono plus colour card in old systems worked because their BIOS occupied different addresses. All VGA cards occupy same BIOS address space. So only one can be primary, they can't work together at low level the same way. Specific drivers for OS could allow it, but that would require one driver written for both cards/chips, think Appian Jeronimo, 3Dfx Voodoo 5 or ATi Rage Fury Maxx (or some older, rarer things in Win3.x era, like Miro's dual S3 cards). Two unrelated cards would need at least Win2k in Windows world.

Linux has other possibilities, although I remember Xinerama (the X extension that offered it) as a collossal headache 20 years ago tbh.

Win98 supported it too. I remember it being a situation where PCs were 10 years behind the Macintosh (which supported monitors since the II I think?) likely due to multiple generic cards not being able to exist on ISA.
Another time this came up, someone mentioned that ELSA made a lot of ISA video cards designed with customizable addresses to support multiple monitors

Reply 6 of 7, by dionb

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jakethompson1 wrote on 2021-08-01, 22:46:
dionb wrote on 2021-08-01, 20:37:

Mono plus colour card in old systems worked because their BIOS occupied different addresses. All VGA cards occupy same BIOS address space. So only one can be primary, they can't work together at low level the same way. Specific drivers for OS could allow it, but that would require one driver written for both cards/chips, think Appian Jeronimo, 3Dfx Voodoo 5 or ATi Rage Fury Maxx (or some older, rarer things in Win3.x era, like Miro's dual S3 cards). Two unrelated cards would need at least Win2k in Windows world.

Linux has other possibilities, although I remember Xinerama (the X extension that offered it) as a collossal headache 20 years ago tbh.

Win98 supported it too. I remember it being a situation where PCs were 10 years behind the Macintosh (which supported monitors since the II I think?) likely due to multiple generic cards not being able to exist on ISA.
Another time this came up, someone mentioned that ELSA made a lot of ISA video cards designed with customizable addresses to support multiple monitors

Iirc Win98 only supported one display driver at a time, so it would work, but only with the same chipset.

Reply 7 of 7, by chinny22

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98SE definitely does. but never tried anything earlier.
I've a GF Ti4600 as the primary paired with a Voodoo 3 2000 but your right the 2nd card is ignored until windows drivers are loaded.
The V3 even displays a message 1/2 way though windows loading saying something along the lines of "the driver is successfully loaded, to enable device go to desktop properties and extend desktop"

BIOS usually has an option what video card search or primary option. Something like AGP/PCI/ISA first one in the list decides which shows the pre OS level screens.