Dual Video Card Ignorance

[Dichotomy]

No I'm not planning to upgrade or even touch anything on the work TD did on my box but I'm seeing a lot of set ups with dual video cards and I'm wondering what this brings to your computer?   What, if any, issues might there be with this configuration? And any other information you guys can impart. 

Thanks in advance.

[Spikes]

There have been said to be some compatibility issues with certain games with CFX and SLI but I have CFX 5770s and haven't encountered anything in particular that causes problems. It just boosts your performance.

[Dragon]

Sometimes it's just better to have 2 to play with.

[SIK1]

This is what I understand about dual vid cards.

There are two types; SLI for the NVidia cards, and Crossfire for the ATI cards. Yor mobo has to be configured to run one or the other.

I've heard that there is some issue with the SLI cards and not being able to run with v-sync on. 

Also from what I've read the performance increase is not all that great. I hear numbers like 10-15% increase over a single card, and of course your power consumption as well as heat output doubles for the video cards.
Most people seem to feel that you are better off stepping up to a single card comparable in price to what two cards would cost.

[Chalenge]

There USED to be an issue with XP and SLI. No longer true.
There IS an issue with some games like RoF with SLI due to a problem with VISTA.
The performance increase with the older SLI cards was something like 10-23%. Newer cards (4xx and 5xx) are more like 80-100% increase depending on the game and your settings. 100% is actually dependant upon very heavy post-processing settings. If you do no additional post-processing then the performance increase is minimal.
With AH you are better off buying a higher performing single card (480 or 580) than you are a less powerful card and using SLI. As you move forward and the cards come down in price you can add a second card for a performance increase rather than buying a more expensive replacement. AH DOES NOT need an SLI setup with anything like a 480 or 580 card because a single card will do everything given that you have a system to go along with the card.
My favorite setup is two GTX 580s in SLI with an 8800 GT for PhysX processing however the power requirements are beyond a typical PSU and pricewise this is definately not for everyone. Besides... it is much better to have a more powerful processer and faster memory than it is to have a multi-bang (cards or monitors) video system.

[Dichotomy]

Thanks Chalenge.. like I said I'm really happy with the way my comp runs the game and looks.  Now I'm tossing my spare change in a coffee can so I can get a new one from TD this year, some time, hopefully.

[Doctahg]

One of the best things about SLI are they make it possible to run special effects at higher resolutions.  I have a 30" monitor so it allows me to run with AA and AF on very high at 2500x1600. 

[Reaper90]

edit: found the answer to that question