Although we already reviewed the EVGA GTX 260 by itself last year, it would be unfair to use those benchmark results to compare with now. So for all the testing that will be done with both cards in SLI, I've first made the runs with just my original card by itself. The hardware used in both configurations is the same, as is the operating system and driver version, as detailed below.
AMD Phenom-II X3 720BE @ 3.6GHz
XFX 750a SLI - 1x16 or 2x8 PCIe
2x2GB OCZ Fatal1ty PC2-6400
Silverstone Decathlon 750W
Vista Ultimate 32bit
Forceware 190.62 WHQL
The nVidia 750a chipset lacks the dedicated nForce 200 PCIe bridge found on the higher-level 780a and 980a boards. Thus SLI bandwidth is limited by splitting the single 16x PCIe 2.0 slot into two 8x sets of lanes. Note that GPUZ detects the dual-SLI configuration and the fact that the cards are at only 8x speed. While this may sound counterproductive to run double the number of cards at half the amount of bandwidth available to each, in practice it typically results in only a minor performance loss compared to both slots being at full 16x capacity. From what I've seen the hit is typically around 5%.
Before installing the second card, the 750a must first be manually set to run in 2x8 SLI mode using a series of jumper pins found on the motherboard. In this XFX implementation, these pin sections are labeled JSLI1 through 4, and the four jumper blocks must be removed from their default 1-2 setting to the 2-3 position. The new card can then be installed and the bridge clip added to link the two together. The GTX 260, like all GT200 core cards, supports Tri-SLI, which is why each card has two sets of "fingers" to connect to. Only one is needed for Dual-SLI mode.
To provide enough juice for these cards, two 6-pin PCIe power connections must be made to each. Although the GTX 260 is only rated at 182W, each 6-pin PCIe can handle 75W with an additional 75W passed through the slot, for a combined maximum ceiling of 225W. Because of this, generally only power supplies rated at 700W or better will possess the necessary cabling for four 6-pin PCIe connections. While you can make due with Molex-to-PCIe adapters, depending on how much wattage your processor and other system components draw I would not recommend using any power supply with less than 600W available on the +12v rail, even more if the rails are divided. As you can see from the chart above, a dual GTX 260 system exceeds 500W under GPU load, and although the OCCT stress test used to generate these conditions also puts some load on the CPU as well, adding a 100% utilization on the CPU would easily top 600W combined.
The EVGA Precision utility can monitor temperature readings from both cards as well as provide manual clock and fan speed control. Keep in mind that any adjustments made will apply to both cards, they can not be controlled separately. If you are thinking of overclocking the cards this is another reason it is better to get a matched pair. For benchmark purposes however I will be leaving the cards at stock clocks for both single and dual SLI testing.
Continue ahead to some Futuremark benching.