We then measured motherboard consumption with an ammeter that gave readings of the different lines on the ATX block. This allowed us to deduct the processor consumption which arrives via the ATX12V as well as that of other peripherals directly connected to the power supply. Tests were carried out with a Q6600, 8800 GTX and 2x1 GB of DDR3-1066.
Compared to a X38, the reference nForce 790i SLI motherboard had 69.8w in stand-by and 74.5w in load. This is power consumption that is 11.4 and 8.4w higher, respectively, than a X38. It’s a notable difference but still remains reasonable.
Overclocking – CPU
Moving on to overclocking the chipset with a Core 2 QX9770, we only give you the frequencies that were validated by four 15 minute sessions of Prime95.
With the nForce 790i SLI, we had to increase chipset voltage starting at FSB1640 to finally attain FSB1800 at 1.5V. The X38 reaches the same limit but we only had to increase power at this last FSB figure. Finally, the nForce 790i Ultra SLI which equips the ASUS motherboard didn’t need a voltage increase to reach the same limit. Does the difference come from the chipset, which is supposed to be better for overclocking, the bios, or motherboard? It’s difficult to say.
Otherwise, we noticed some bizarre behavior on the reference motherboard and ASUSTeK model: with a Q6600 (Stepping B3), we couldn’t go above FSB1400! Beyond this value, the reference version wouldn’t boot and the ASUSTeK deactivated the two last CPU cores. Results obtained with a QX6850 (still a 65nm but with a FSB1333 by default) were better with FSB1760 obtained on the ASUSTeK while it was unstable in FSB1600. With the reference model, we couldn’t go above FSB1560 in these conditions. Given the results obtained with the QX9770, we believe this is only a problem with the bios.
Overclocking – Memory
We end the testing by looking at increases in frequency with four DDR3 modules, here Kingston PC3-14400 CL8s. We made the transition into synchronous mode, FSB1600/DDR3-1600, and then increased frequency with 2 and then 4 modules.
As you can see, the nForce 790i SLI has a few problems in this area because installing the four modules means difficulty in increasing frequency. Otherwise, with the X38 results are the same with 2 or 4 modules and this also goes for the nForce 790i Ultra SLI. Here again, it’s hard to know if the motherboard, bios or chipset is responsible.