Look boys - a single card IMO always places ahead of dual cards in value. I don't care what benchmark you show me, a top-of-the-line single card is always better for general usage.
Here's why:
- not every game supports, or runs SLI/CF bug free
- not every game scales well with SLI/CF
- you need to push it with higher work loads to see most of the benefit. Sometimes, you're just not running a high enough resolution to make a difference versus a single card
- 2x lower value cards usually have less VRAM, which in a lot of cases is a bottleneck in itself for higher resolution. You're kind of fighting fire with fire if that make sense
- 2x the heat and power during load and idle (though ATI does more nifty throttling on the second GPU, there's still a 2nd GPU plugged in)
- do you really need 2 entire GPU's present in your system? What a waste.
Need I say more? I can't believe how many people are falling for the SLI bullshit (pardon my french). It's 90% marketing ploy, 10% useful in very specific scenarios.
I don't care what two cards are cheaper when SLI'ed for so called better performance - I'll take my lone GTX580 any day.
Even if it doesn't scale well every time, it can often scale well enough to outperform a single more expensive card.
It doesn't have that much less VRAM, and VRAM requirements depend more on resolution than anything. 2xHD6850 CF vs HD5870 (for example) you still have 1GB RAM per GPU, where's the loss?
Only vs a GTX480 or 580 does it become potentially significant, and only at some resolutions.
2x the power? Yes, of a single equivalent card. 2x the power of a higher end card? Hell no. Sometimes it can even use less power than a single higher end card (at load).
It's not for everyone, but it is often much better value than a single high end card, MUCH better, by often being cheaper AND faster AND it can even use less power. And if you play mainly a few games, then poor scaling in some games isn't a problem.
The last 4 games I've played? Team Fortress 2, Mafia 2, Starcraft 2 and Stalker COP. All of which either don't scale because they are CPU limited on my system, or are big titles and therefore do scale. Extending it, I'd be adding Mass Effect 2, BFBC2 and Dragon Age. All of which are big titles and AFAIK (not that I care since I got a P43 motherboard) are supported by multi-GPU solutions due to their AAA status.
It obviously has caveats, but so do most things.
Caveats of a single high end card?
-Power use (at least at the highest end in single GPU cards, particularly GTX480)
-Cost
Cost being the most significant one.
A single card is pretty much always more appealing, except it's also almost always more expensive, and that's pretty much the entire issue. SLI/CF offers the value proposition relative to a single GPU card, and that's what it's about. You buy it for high performance at a lower price, otherwise we'd all be running GTX580's, maybe even in SLI.
There is no single brush with which you can paint everyone, since everyone has their own situation and preferences. "General use" is all well and good until you start to ask what "general use" is to a gamer. It's playing their specific games, for which multi-GPU may work brilliantly every time and offer 25% more performance at 75% of the cost of a single GPU card.