Crossfire/SLI - How and What?

[BWLAF]

I have a couple of questions concerning Crossfire/SLI configurations.

What exactly do they do? How do they differ from just having two video cards?

How do they do this? What is the technology involved?

How do they need to be configured to do this? What do you need to do?

What are the advantages/disadvantages of Crossfire/SLI vs dual video cards?

What are the advantages/disadvantages of Crossfire vs SLI?

Thanks in advance, it's something I've always struggled to understand.

LAF

 

[Yami]

What exactly do they do?

They allow you to double your GPU processing power for about half the price of buying an equivalently powerful GPU.
For example, I have a GTX260 in my system. Two GTX260s are roughly as powerful as, say, an HD5870 (not sure on the accuracy there, just using it as an example).
A new GTX260 will cost me just over £100, whereas a HD5870 is over £300. By buying a second GTX260, I then have the same graphics power as an HD5870 for a third of the price.

How do they differ from just having two video cards?

If you just have two video cards then you can only use one at once for things like gaming, leaving the other card to do nothing. Having SLI/XFire lets you use multiple cards for the same process.

How do they do this? What is the technology involved?

The GPUs are connected with an SLI/XFire bridge. The more technical stuff is rather beyond me at the moment, Wikipedia should probably give you plenty of technical information, as might other members here.

What are the advantages/disadvantages of Crossfire vs SLI?

SLI used to get you a better performance boost from adding a second card but they're both pretty much equal now.

What are the advantages/disadvantages of Crossfire/SLI vs dual video cards?

Allows you to use multiple cards for the same thing, whereas just two video cards won't. One old disadvantage was that you couldn't use the video outputs on extra cards but I believe that's gone now.

 

[BWLAF]

Very informative, thank you