After digging around in the OC Tweaker UI and getting mixed results with the ASRock Z97 Extreme6’s “Optimized CPU OC” settings, I went ahead and manually edited the overclock settings. I initially set the multiplier option to 42, and then started a conservative climb to 44. As I went along, I tested different multiplier/voltage settings by using Prime95 to generate a workload and RealTemp to see how hot the CPU was getting. Once I was able to settle on a combination that kept the CPU peaking in the low 90-degree C range, I made sure that I was happy with the 3.5GHz Core i5-4690K running at 4.4GHz and 1.24V by tacking on an additional workload – in this case, our Tom’s Hardware 3ds benchmark.
For the memory, I just ended up using the OC Tweaker’s XMP profile to set my DRAM. The time to get Big Build ready for the quarter's SBM was getting shorter, so I had to put off the memory overclocking and re-prioritize. At that point, I had bigger fish to fry…
Next, I needed to overclock the Gigabyte GeForce GTX 980 graphics card using Gigabyte’s OC Guru UI. This took a little tinkering. I just so happened to start the tests with high memory and GPU clocks, and from there I slowly dropped clock rate until I found something stable in 3DMark’s Fire Strike benchmark. It took a few tries, but I ended up with the memory clock set to 8000 MT/s and the GPU base clock at 1365MHz. Lastly, I set the GPU fans to manual and pushed them to their fastest speeds. After one last run of Fire Strike, I started the automated benchmarks and headed home for a nap.
In its overclocked state, Big Build ran the gaming benchmarks pretty smoothly. There were a couple of points when I was testing with Grid 2 that Windows crashed, so I dropped the memory to 7900 MT/s and the GPU 1350MHz. After that, the benchmarks went fine and I was ready to move on to the thermal and power tests. Similar to what I did when I was setting up the host processor the night before, I used Prime95 to stress the machine. Suddenly, I started getting one blue screen after another. It didn’t seem like a complete hardware failure since the machine didn’t immediately reboot and go into POST; it would just blue-screen and tell me that that it would eventually reboot itself.
I suspected a combination of factors. Going back to the default CPU clock rate ultimately fixed the problem, and raising and lowering the GPU’s overclock settings didn’t seem to keep the machine running at the higher CPU clock setting. I was able to stabilize Big Build’s power and thermal testing by running the core speed at 4.2GHz and dropping the voltage down to 1.235V. Afterwards, I got my power and thermal numbers and put Big Build back into its prior 4.4GHz/1.24V configuration and reran the graphics benchmarks to confirm stability.
I also want to add some extra notes about getting past the problem I had with the power/thermal testing. I was able to stretch the amount of time between Windows crashing on me by disabling Nvidia’s Surround feature. I also reinstalled the Nvidia drivers after one particular crash and was able to run stably for a little while longer. Lastly, and interestingly enough, I noticed the CPU wasn’t overheating when the OS blue-screened; RealTemp usually reported that the processor was in the mid to high 80 degree-range whenever it crashed.