Well, I took a look at that mobo's reviews, and didn't see anyone saying that it doesn't work wit SLI--perhaps I missed it. But after looking at a few reviews of the mobo through a google search (a great way to find reviews of any mobo you're looking at), it seems as if it's a Crossfire board, not an SLI board.

If it were me, I'd get this board: Newegg.com - ASUS P5N32-SLI Premium/WiFi-AP ATX Intel Motherboard - Retail


Asus is a great brand, and this board looks like a great board (have never used it, but reviews are great), and is an SLI board. There are a few others, here's the url for the main result page for SLI/C2D boards from newegg: Newegg.com - Search Results for sli

I'm sure there are others if you take a longer look, but I don't have the time to do that right now, that's just the result of a quick search.

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AMD Athlon 64 X2 4400+ (@2.6 GHz)
2x1GB OCZ Spec. Ops. PC3200
ASRock Dual939-SATA2
Antec TruePower 550 watt PSU
80 GB Seagate Barracuda SATA 7200 rpm
300 GB Seagate Barracuda SATA 7200 rpm
120 GB Maxtor ATA/133 7200 rpm
ATI Radeon x1950 Pro

I found this mobo http://www.newegg.com/Product/Produc...82E16813131071. It says it is SLI compatible, and that it runs at 8x on each in SLI. If I got 2 7900GT's would that severely effect performance in games?

Well, I'm not 100% sure, but I think that the max bandwidth you can have through a PCI-E 16x interface is the speed of the interface (in this case 16x) divided by the number of devices on the interface. So the 16x speed would be divided by 2 cards to give 8x each, but total, the speed is still 16x--the performance boost is because one card can render odd scanlines and the other card can render the even scanlines--so twice the number of scanlines can be rendered in the same time, but the actual throughput of the bus is still limited to x16, so you're limited by the clock speed of a single gpu core).

I've gone back and forth on whether a 2x gfx card setup is worth it. I've found that 2 cards in SLI aren't as good as one better card that has twice the RAM (like 2 7900GT's vs. a single 7950gtx). I don't think it 2 is better than 1 because typically, if you have a good graphics card, the CPU becomes the bottleneck of the system when gaming anyway. So the way I understand it, all that really happens is you essentially double the amount of VRAM that you can use--so if you're limited by the amount of AA and AF you can use in a game, it will be better with the addition of a second card, but realistically probably not to the point that you'll see a noticeable performance increase in gameplay--the calculated FPS's might be higher, but your eye can't really distinguish much past 30 FPS's anyway). But as far as effective clock speed of a 2x gfx card setup goes, it's the same as the clock speed of one of the gfx cores--very similar to how a dual-core CPU is not twice the speed of one of the cores. That means that if you've maxed out AA and AF, then FPS's won't increase with the addition of a second card. But since you've doubled the RAM, AA and AF will look better and possibly provide smoother gameplay (though this theoretical performance increase is only because there is more RAM--not because the clock speed is faster). So doubling the RAM is a good upgrade, but you likely won't notice it if you already have a good card (at least 256 MB with a good chipset--like your 7900GT). It's a waste of money in my opinion to go SLI or crossfire. I'd say just get a 7900GT for now (and they overclock very nicely) and save your money for after DX10 has been released and proven, and after there are more options for DX10 cards.

__________________
AMD Athlon 64 X2 4400+ (@2.6 GHz)
2x1GB OCZ Spec. Ops. PC3200
ASRock Dual939-SATA2
Antec TruePower 550 watt PSU
80 GB Seagate Barracuda SATA 7200 rpm
300 GB Seagate Barracuda SATA 7200 rpm
120 GB Maxtor ATA/133 7200 rpm
ATI Radeon x1950 Pro

Ok, my new setup will be SLI compatible for both mobo and PSU. I'm gonna start with one 7900GT and then get a 8800GTX when I get some more money. And then if DX10 is amazing I might even go SLI on the 8800GTX.

this is fun reading old threads and then realizing how much more the people know now....