It was necessary to fire up the Gigabyte with a QX9650 and then install Beta BIOS F4A before I could switch to the QX9770. The new BIOS knocked out a fair few of the overclocking options and in particular the front side bus was locked at the stock speed although I could adjust voltages and clock multipliers to my heart's content.
Initial test runs with PCMark05 and POV-Ray showed that QX9770 had a small advantage over QX9650 but that's exactly what you'd expect, as the 3.20GHz QX9770 has a 6.67 percent lead over the 3.00GHz QX9650. If you normalize the two sets of figures there's nothing to choose between the two processors although the QX9650 uses rather less power than the QX9770.
When it comes to overclocking I was able to bump up the multiplier on the QX9770 to get a speed of 3.60GHz without making any other adjustments but the next step of 4.00GHz took a little work as the system was unstable until I raised the Northbridge voltage by 0.05V and the CPU voltage by 0.2V.
The step up from 3.20GHz to 3.60GHz yielded a performance increase that was directly in line with the clock speed but the 4.00GHz jump increased the power draw enormously while performance was less linear. I was using a Zalman CNPS8000 cooler that is very quiet and it managed to keep the 4.00GHz overclock under control despite the ludicrous amount of power pumping through the motherboard.
Just for larks I ran the CPU benchmark that is built in to Crysis however the test system was clearly limited by the Radeon HD 3850 graphics card so the processor speed had no effect on the frame rate.
While I was unable to overclock the QX9650 on the Gigabyte with the Beta BIOS I've included a set of figures that I got on an Asus Maximus Formula SE with a GeForce 8600 GTS graphics card a couple of weeks back. You need to read the numbers carefully as the two platforms are not directly comparable, but if you study the PCMark05 CPU test result for the QX9770 at 3.60GHz and the QX9650 at 3.69GHz it is clear that the two processors are delivering a near-identical workload and the same is true in POV-Ray.
Intel's latest and greatest processor gives us a good idea what to expect from the 1,600MHz FSB in 2008 and while it's very encouraging we have to wonder exactly why it was so keen to deliver samples to reviewers before the X48 chipset was ready.