System Assembly And Over-Clocking
We ran into two issues as we were putting this system together.
First, the motherboard’s rear I/O panel cover doesn't line up with the USB and PS/2 ports on the far left. We’re not sure why. It seems like the holes aren't placed perfectly, and we suspect the recess on the Logisys Optimus II case isn’t square with the motherboard. Whatever the cause, we had to install our motherboard without its panel in place (irritating for the perfectionists on our crew).
Secondly, we had a problem fitting the huge Sapphire Radeon HD 7970 OC into our case. It can be made to fit, and it does work. But the very end of the cooler's shroud pushes against the chassis, and we’re not comfortable with that. If you plan to buy this extra-long and extra-wide graphics card, take some measurements first to make sure it fits inside the chassis of your choice.
Overclocking
In our last mid-range build, we were unable to force the Core i5-2400’s maximum 38x multiplier due to BIOS limitations. Gigabyte's P67X-UD3 doesn’t suffer from those same constraints, though it turns out that the difference is mostly theoretical.
We were able to set a 38x ratio. However, it's only used in single-threaded workloads. In fact, we found it very rare for our build to run at 3.8 GHz at all, even when Prime95 was set to push a single core. It instead bounced between 3.6 and 3.8 GHz. We turned off CPU thermal monitoring in the BIOS and increased the Turbo Boost power limit to 200 W, but those changes yielded very little benefit. The only way to get 3.8 GHz reliably was to set processor affinity to a single core in Windows' task manager. Applications optimized for two or three threads tended to run at 3.7 GHz, and any software able to exploit all four cores ran at 3.6 GHz.
Because our application suite is heavily threaded, we expect to see very little difference between the new results and the ones from the previous build, although we're still hoping that the additional memory bandwidth attributable to a second channel will help in some instances. Then again, losing the SSD probably won't help this quarter's build.
Sapphire’s Radeon HD 7970 OC proves to be fairly tunable, although the newest version of the company’s Trixx overclocking utility has some problems. We ended up with a maximum core overclock of 1125 MHz and a memory frequency of 1650 MHz, achieved with a 1.2 V setting in MSI's excellent Afterburner tool.
