Power-Hungry, Hot, And Big
Performance aside, there are a few other considerations in comparing one card to two.
The first is physical size. This really only works if you have the platform and available PCI Express slots for it. It might be worth paying a little extra for a GeForce GTX 295 in order to save two expansion slots worth of space. Or, if your motherboard isn’t SLI-certified, taking the single-card route saves you from an upgrade.
Next up is heat. We know from experience that running three GeForce GTX 280s is difficult if you don’t have enough airflow. The cards have virtually zero room between them, and two of three are left trying to suck air through thin gaps between the boards. The only way to make thermal management any more difficult is smashing a pair of GPUs onto a pair of PCBs wedged into a double-slot package.
The GeForce GTX 295 pulls it off though, and at roughly the same core temperatures as the hottest card in a GeForce GTX 275 SLI arrangement. Note that, while the GTX 295 does exhaust much of its heated air out the card’s back-panel, an open top means there will also be a fair amount of recirculation in a closed chassis. In contrast, the GTX 275s blow everything out the back.
You would think that, given their identical core and memory configurations, two GeForce GTX 275s would gobble as much power as a GeForce GTX 295. In fact, that’s not the case at all. Consumption is close at idle, varying by about 20W. But under load, the two GTX 275s use almost 100W more than the taxed GTX 295.
So, as we start looking at numbers, bear in mind that two GeForce GTX 275s will eat up twice as many expansion slots, get warmer, and use more power than a single GeForce GTX 295. In return, you can buy those 275s for about $20 less than a regularly-priced 295 (providing you can find one for sale, that is).
Now let’s factor performance into the equation. Remember that the GPUs on a GeForce GTX 295 run at 576 MHz (with 1,242 MHz shaders), while the memory clock is set to 998 MHz (1,998 MT/s effective). Stock GeForce GTX 275s run at 633 MHz (1,404 MHz shaders) with 1,134 MHz memory (2,268 MT/s). That’s a significant theoretical advantage for the single-GPU cards. Onward!
