Re: Triple Monitor Question
Eyefinity is enabled on all 5xxx and 6xxx cards. You can have anywhere from 2 to 6 displays in an Eyefinity group (1x2, 2x1, 1x3, 3x1, 1x4, 4x1, 2x2, 3x2, 2x3, probably others as well). I have 3 1080p Dell ST2210's in 1x3 configuration (though usually I use them separated, but for gaming I use Eyefinity Group 1x3 mode).
The normal 5870s can only go from 2 to 3 in an Eyefinity group because they can only run 3 monitors. The 6xxx cards may support 4 monitors (don't know for sure) and if they have a 6-MiniDisplayPort version it would likely support 6 monitors (as does the 5870 Eyefinity x6).
With CrossFire Enabled:
Only primary card's monitors work
--If primary is normal, up to a 3 monitor Eyefinity group or 3 individual monitors
--If primary is x6, up to a 6 monitor Eyefinity group or 6 individual monitors or a combination thereof
All CrossFire'd GPUs render the same scene - must have a CrossFire bridge connecting all CrossFire'd GPUs
If CrossFireX Disabled:
All cards' monitor outputs are enabled
-Multiple Eyefinity groups can be set up - but only out of monitors connected to the same card
-Normal multi-monitor groups (independent monitors) can be arranged without regard to what card they're on
-Graphics rendering power is limited to what GPU the monitor is attached to
Cards without monitors attached may not be available for GPU computing uses
Playing a game on one monitor will only use the GPU it is attached to, the other GPU's will idle.
You may mix GPU's from different series normally, but CrossFire'd GPU's must be from the same series. If you put a 6970 and a 5870 in the same PC both will work, but the monitors on the 6970 will have better performance due to the 6970 rendering their output.
Also note that it is very easy to enable and disable CrossFireX on the fly. If you want to put your main Eyefinity (say 3 monitor) setup on your primary card for gaming but put your TV or other non-gaming monitor on your secondary card, simply switch off CrossFireX when you're done gaming to use the monitors on the secondary card, the hardware CrossFire bridge may remain in place without issue. Just note that turning off CrossFireX will limit you to single-GPU rendering.