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I'm considering installing two graphics cards in my retro gaming setup (one AGP and one PCI) and was wondering if there are any drawbacks to doing so?

The main things I'm thinking about are power requirements (I guess a card will draw little to no power when not in use?) and driver considerations - having nVIDIA and 3dfx drivers installed at the same time.

The two cards are a Voodoo3 2000 and a GeForce2 MX and the other specs are a 900MHz Athlon, 256MB PC133, Soundblaster AWE64 Gold, 1x IDE HDD and a CD-ROM drive, with a 250 watt FSP power supply (20A on 3.3V, 25A on 5V, 14A on +12V and 0.4A on -12V).

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    AGP and PCI are now officially "retro"? ;-)
    – dave
    Commented Mar 13, 2020 at 13:07
  • @another-dave well good luck finding them on a modern motherboard :-) but yeah, granted compared to ISA slots and stone tablets etc they're not that retro! (I do have an ISA slot in this setup and it's actually in use so all due respect to ISA)
    – Sam
    Commented Mar 13, 2020 at 13:11
  • Since AGP was pretty much obsoleted and gone from most motherboards and GPUs in 2010 - 10 years ago - I think they can safely be called retro. PCI was similarly replaced by PCIe around the same timeframe.
    – Mavrik
    Commented Mar 16, 2020 at 13:10

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With only a 250W power supply you may be pushing the limit with two video cards, but it's hard to be sure. Neither of the video cards you're planning on using are particularly power hungry. I suspect nether comes with a fan, and the GeForce2 MX may not even have a heat sink. The PCI connector can only supply 25W and I believe the AGP 1.0 interface had the same limit, so this sets an upper limit on what these cards can use, but it's likely both cards used significantly less power.

Since I assume you're using an ATX power supply, if necessary you can just replace it with a newer bigger one. You'll have to look closely at the specs though, since modern supplies use the +12V rails to supply most of their power, and may actually supply less power through the +3.3V and +5V rails then what you're using now. A modern supply with also lack -5V, but only really ancient hardware used it, nothing in your PC will need it.

Drivers shouldn't be a problem, since the video cards are made by two different manufacturers. Using two video cards from the same manufacturer often didn't work on Windows 98, but you should be fine with a 3dfx and a Nvidia card installed at the same time.

The VGA port conflict TEMLIB mentioned should't be a problem, as only the video card you designate as the primary video card in the BIOS setup will provide VGA backwards compatibility. The secondary video card will have its VGA compatibility disabled. The primary card will be the one that's used while booting, and it should be the one Windows 98 uses as the primary monitor.

Since you're only using one monitor and since most games didn't give a choice of what display adapter to use, you'll probably have to select which video card you want to use by rebooting your PC and changing which video card is primary in the BIOS. I'm not sure how Windows 98 multi-monitor support will deal with this. Ideally it'll treat your secondary display as disabled, since it doesn't have a monitor connected to it. If not you'll want to manually disable the second display, otherwise your mouse pointer will end up getting lost on it.

You might also run into Windows 98 needing to reconfigure things a startup after switching which video card is primary and asking you to reboot multiple times. In that case I'd would just keep saying "no" until all the pop ups are done and then rebooting just once.

I just did a quick check of using Windows 98 two video cards, an AGP Radeon 9550 and PCI Rage II+ and it worked fine as far as I tested. I was able to use both simultaneously, though I had to manually enable the Rage II+ as a second monitor. Despite being from the same manufacturer there were no driver conflicts, as they're from two very different generations. I didn't test it with any games, as I only have DOS games installed on that PC.

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  • You are correct about no fans (both have heatsinks). Appreciate the heads up on the potential ghost monitor issue. I'll give this a shot then and report back if there are issues (else other readers can safely assume it all worked nicely).
    – Sam
    Commented Mar 13, 2020 at 13:36
  • That description of Win98 not being able to deal with both cards simultaneously and having to reboot and reconfigure is plenty to dissuade me from two separate video cards. I currently use a Voodoo2, which requires a second 2D video card and acts as a pass-through when not in use. This works very well with Win98.
    – Brian H
    Commented Mar 13, 2020 at 14:20
  • @BrianH that's a great card for 1998 games but not so much for 2001 games so depends what you're wanting to play really.
    – Sam
    Commented Mar 13, 2020 at 14:54
  • @Sam Very true. I've been mainly focused on finding one machine that can adequately play most games from the 90s, which is difficult enough.
    – Brian H
    Commented Mar 13, 2020 at 15:44
  • @BrianH sounds like you're off to a solid start with the Voodoo2! Another in SLI or a Voodoo3 should comfortably handle even the more demanding titles of 1999. What's the 2D card you're using?
    – Sam
    Commented Mar 13, 2020 at 15:54
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That's tricky. PC video cards had to be compatible with old CGA/MGA/EGA/VGA standards over ISA which didn't offer plug and play and remapping.

Your two video cards may be incompatible, conflicting over accesses to registers, for example the palette or Video RAM in A0000.

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  • Well I think you know a lot more about this than I do, but I don't understand what 80s technologies like ISA, CGA and EGA have to do with turn-of-the-century high-res high-colour depth 3D PCI / AGP cards? If we're just talking about legacy modes for DOS applications then I'm not too concerned about that (I just use DOSBox emulator on my modern PC for DOS stuff). It's Windows 98 gaming that I'm thinking more about (and power requirements - I know these cards don't draw much but it's also a pretty small PSU and fairly hungry CPU by the standards of the time).
    – Sam
    Commented Mar 13, 2020 at 9:04
  • @Sam Even the latest PCI-Express video cards are VGA backwards compatible, and so use the standard and fixed VGA memory addresses (which are also backwards compatible with the older EGA, CGA and MDA cards). However, if you plug two or more PCI-Express cards into a computer, one card gets designated the primary video card and only that card provides VGA backwards compatibility. That card is also the one used when booting the system. The VGA comparability in the other cards is disabled.
    – user722
    Commented Mar 13, 2020 at 11:48
  • @RossRidge that primary card option is why I was thinking it might be doable - I have to choose AGP or PCI to boot from in the BIOS (display init first or whatever that option is called) and then plug my monitor into that card so you'd think the BIOS would present a single primary card to the OS to avoid resource conflicts?
    – Sam
    Commented Mar 13, 2020 at 12:00
  • @Sam Yes, you shouldn't have any resource conflicts, but if you only have one monitor there's not much point in installing two video cards.
    – user722
    Commented Mar 13, 2020 at 12:03
  • @RossRidge it's for performance and compatibility reasons. Some 2000-2001 games are a bit demanding for the Voodoo and are noticeably smoother on the GeForce (e.g. Red Faction, Undying). Others, like Thief and Outlaws, look much nicer on Voodoo (any game limited to 16-bit colour really) and don't need the added muscle of the GeForce. I'd rather not be swapping cards in and out all the time for different games (wear on the AGP port and on the card contacts, and just inconvenience).
    – Sam
    Commented Mar 13, 2020 at 12:06

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