The SB750 retains the same features as the earlier SB700 that was released with the 780G, but it adds the ACC functionality which promises to increase the potential overclocking headroom of the Phenom processors (Athlon X2s do not benefit from ACC). Advanced Clock Calibration is a functionality which uses a direct connection between the southbridge and the CPU to internally adjust settings to allow for (apparently) looser internal timings which will benefit overclocking. Underclockers will also see a benefit here, as enabling ACC with specific settings will allow users to dial down the voltage at the CPU’s stock speed a bit more than usual, or significantly underclock the processor and really get the voltage and power consumption down. This is probably the feature that will sell these boards the most, and considering the price of the 9850 and 9950 Phenom processors, this could turn into a nice budget enthusiast platform.
Gaming and video performance of the 790GX is pretty astonishing considering it is an integrated part. I have played a number of games and watched some High Def movies on the system I am testing, and it just goes about its business like no other integrated part before it. The extra 200 MHz the 790GX has over the 780G is further complimented by the addition of the high speed SidePort Memory. Though the memory bus is only 16 bits, the addition of 2.66 GB/sec of additional bandwidth, which is also low latency, really enhances what is further given by the CPU and the dual channel memory controller going to main memory. At stock speeds with a Phenom 9950 running 4 GB of PC6400 memory at 4:4:4:12 timings, 3D Mark 2006 scored 2137, while 3D Mark 2005 had an impressive 4552 (which is dangerously close to what a GeForce 6800 GT or a Radeon X800 XL was able to score). The Gigabyte board I am testing features HDMI and DVI with HDCP, so high definition playback should not be an issue. It also features the full Avivo HD + UVD functionality, so playback at up to 1080P is nice and smooth.
I will have the full article done tonight, so be sure to check back later to see how well ACC did with a 9950 that had problems at 3 GHz on a 790FX motherboard with air cooling.