The 6990 in high power mode is 450 watts by itself. ONE FAN cools it and it's a large card. So, I would think someone would need at least an 850 watt PS to handle that with a good system besides. The 590 is about 375 watts. Add another as you suggested and there goes the single PCIe PS argument out the window. Also, to add another 225+ watt card you need a better PS anyway! So the power supply argument is moot... they have what is needed or they don't.
6970 and 580 are about 250 watts spread over a larger physical area (combined) and using a pair of them is about the same cost as using one larger dual card but a little more power in total. BUT, you get double the cooling systems with double the fans and lower power density.
I have to say that anyone buying these cards is probably not going to put them into a Pentium 3 or K6 system... rather they probably have at least a modern dual core system with at least 2 gig mem. Less than that is pure silly since they will be terribly CPU bottle-necked at high resolutions.
I'm glad you agree about the realestate/PCIe issue, it is a concern MAYBE.
I think these cards are aimed at the HIGH END user and likely they have systems that can handle more than one card. But, with everything else being equal, I suppose it falls to the tiny less significant points to make a decision. But some bits of argument you mention are mutually exclusive!
You can't buy thinking you will add another card later on a marginal PS or because of marginal space or marginal base PC Mobo issues!! Buy a dual GPU on that basis and you are stuck with a single video card option without upgrading something else. That's fine if that is ones intent. Chrome the engine then paint the car eah? You see what I mean? Put any two of some points together and they exclude each other as a basis for making a decision! So, I presume one would decide based on only ONE point. High end system and high end users need not worry!
I stand with my statements, there are legitimate arguments AGAINST dual GPU cards, but having decided to use one, pick your poison!
I see no real argument against what I said, only possible "single point" reasons to decide to go double GPU rather than paired cards in SLI/CF. I sure think whomever buys a dual card won't be disappointed provided their system can handle it!!
We will see how long the boards last. My friend has a 6990 in his system and it's a screamer... I wish him luck and so far so good! (noise is bad, but runs great!!)
Edited by Tex1954 - 6/5/11 at 1:04pm