Power consumption
We measured system power consumption, sans monitor and speakers, at the wall outlet using a Watts Up Pro power meter. Power consumption was measured at idle and under a load consisting of a multi-threaded Cinebench 10 render running in parallel with the "rthdribl" high dynamic range lighting demo.

In testing, we discovered that the BIOS for the GA-P35-DQ6 motherboard we used for our P35/DDR2 system doesn't correctly throttle clock speeds with either C1E or SpeedStep. Older BIOS revisions used to work, but Gigabyte broke something with its last release. That could explain the lower CPU utilization results we saw for the P35 configuration in some of our peripheral testing.

Recent nForce chipsets have been quite power-hungry, and the 780i SLI falls right in line. With an extra nForce 200 chip under the hood, the 780i draws about 7W more power at idle and under load than the 680i SLI. That puts its power consumption much higher than of Intel's P35 and X38 Express chipsets, at least when they're paired with DDR2 memory.

Overclocking
For our overclocking tests, we dropped our CPU multiplier to 6X—its lowest possible value. The memory bus was also maintained at 800MHz to keep our DIMMs running well within their limits at overclocked front-side bus speeds. Next, we turned our attention to the front-side bus, cranking it up and using a combined load of Prime95 and the rthdribl HDR lighting demo to test stability along the way.

When we hit a 450MHz front-side bus, it became necessary to add the 780i's optional chipset fan to keep the system stable under load. But we didn't stop there. The board easily sailed up to 480MHz without the need for extra voltage or additional tweaking. It would go no further, though, and no amount of voltage fiddling or human sacrifice could coax 490MHz from the front-side bus.

480MHz is still quite an overclock and more than enough to run a QX9770 on a 1600MHz quad-pumped bus. However, it's worth noting that we've seen 500 and 510MHz front-side bus speeds with identical hardware on X38 Express boards.

As is always the case with overclocking, your mileage may vary.