Objective: Use 3 monitors attached to two video cards that are the exact same.
Win 7 SP1
2x HD4870x2 (Crossfire Cable connected)
1x LG L227WTG LCD (using native DVI)
2x Dell 17" LCD (one using native DVI connector, one using a VGA cable with a DVI>VGA adapter [I didn't have a third DVI cable])
Driver: 8.951.0 (Dated 3/8/12)
Based on what I've read over the last couple days doing searches, I downloaded the latest ATI/AMD drivers (available a couple days ago) and used Catalyst Control Center to disable Crossfire via software, my understanding being that Crossfire would keep me from using the third monitor.
I then plugged my main display into what had been my primary card, and plugged the two side monitors (the 17"-ers) into the former "secondary" card. IMMEDIATELY when I plugged the first monitor into the other card, the display driver "Stopped responding". When I removed the plug, it recovered.
Here's what I've come to find out: If I plug any two of the 3 into the former "primary" card, they work just fine. But if I plug a third one in, the driver crashes. If I plug any one into the main card and any other into the secondary card, the driver crashes.
How can I attach the third monitor? Do I need to physically disconnect the Crossfire cable from the two cards? I'm okay with switching back and forth using the software for gaming, but I'd rather not disable Crossfire completely.
On my cards I can't use any of the connections on my secondary/tertiary cards until all the ports on my primary are used up. Quite possibly that goes for you too. However you shouldn't have to disable Crossfire for that o.O that's not normal. Something wrong with what you're doing for sure. What ports does your primary card have?
FtsArTek: Both cards are identical. They have 2 DVI ports and one S-video port each. I did fill up both ports on the primary before plugging the third into the second card.
MoNkRar: I cannot switch the slots of the cards due to the liquid-cooling setup currently in place, but thanks for the suggestion.
Both cards seem to function fine when using monitoring software, although one GPU on the primary card gets a bit hotter than I'm comfortable with (90 degrees under load). The other 3 maintain between 45 and 60 under load.
Also, since I updated the drivers, and with just two monitors plugged in using both DVI ports on the primary card, the driver atikmpag.sys will occasionally crash when entering or leaving a game.
The top card (physically) in the system is actually the "secondary" card that I'm trying to plug the third monitor into. The bottom card is the primary card with two DVI outputs to the current monitors. One of the GPUs on that card is getting hot.
NOTE: Since I downgraded to my previous drivers (8.812, 1/4/2011), that GPU has not been getting as hot, and the driver hasn't crashed (yet).