PCIe and PCI bus Nvidia cards in same machine - why do I get slowdown?

[kasakka]

Since I got myself a FullHD television, the two outputs on my GeForce 8800GT 512 MB were not sufficient since I already had two monitors. Because my motherboard doesn't have two PCIe x16 slots I went and bought a PCI bus GeForce 6200 128 MB to get all three monitors running.

I'm using Vista Home Premium SP1 64-bit with 177.92 drivers and three monitors:

1. 1920x1200 (main monitor, connected to 8800GT)
2. 1920x1080 (television/2nd monitor, 8800GT)
3. 1600x1200 (3rd monitor, 6200)

If either graphics card is the only one in the machine everything works fine. The 6200 isn't underpowered to run Aero because it can run for example Quake3 just fine in 1600x1200 (albeit with reduced texture detail due to its limited memory).

Temperatures should be fine, 40C for water cooled 8800, 58C for passive cooled 6200.

But when both cards are connected I get the following problems:

• OpenGL games/programs will run at around 1 fps no matter which graphics card is used.
• Moving/resizing windows on the 3rd monitor (connected to 6200) is sluggish.

Can anyone tell me why this happens and how to fix it?

 

[kasakka]

It seems if I turn off "extend my desktop to this monitor" in Display Settings then OpenGL works as well. The moving/resizing thing happens also with the 6200 as the only enabled graphics card so it seems that it's simply too underpowered. Turning off the transparency effect for windows helps a bit. The OpenGL problem is a weird one.