Today’s build was one of the most challenging overclocks we’ve encountered on a Core i7 system. The most noteworthy issue was overclock-resistant RAM that threw errors so infrequently that it took hours just to find the cause.
Memory that initially appeared eager to run at DDR3-1600 eventually had to be clocked down to DDR3-1400, likely due to increased enclosure heat during gaming sessions. Once again we recommend blower-equipped graphics cards to anyone who can tolerate a little more noise in exchange for a superior overclock.
One setting that points to the memory heat spreaders as a potential problem is that this memory didn’t tolerate our “default overclocking” setting of 1.65 volts. Also notice that the CPU core is set to only 1.30 volts.
The memory worked at CAS 8 after we loosened up its advanced timings a little.
Our final CPU overclock of 4.03 GHz is limited exclusively by voltage, which in turn was limited by heat. The system supported 12 threads of Prime95 at 4.2 GHz and 1.35 V, but only when the graphics cards were idle. Combining FurMark with 11 threads of Prime95 caused heat to increase slowly to the CPU limit, and our goal was 100% stability under all conditions.
It appears our overclocking niggles are numerous, from RAM that gets too hot to graphics cards that exhaust heat into the case and a CPU that runs a little warmer at 1.35 V than our previously-tested Core i7-980X. Switching our fans from mid-speed to high-speed mode made the system howl, while dropping CPU temperatures by only 4° Celsius. But that only lengthened the time it took to overheat by around 50%. This served as further proof that we’d be stuck at 4 GHz with a 1.30 V core limit unless we were willing to make radical alterations to a build that, outside of its overclocking capabilities, appeared to be a fairly solid configuration.
By now a lot of readers who profess extensive knowledge of case design will begin blaming the Antec Three Hundred Illusion. The only problem they'll have in getting us to accept that explanation is that we've used the same case in our June System Builder Marathon, with a pair of even-hotter GTX 470 graphics cards on the same motherboard, and had no such case temperature issues. Overcoming the internally-vented graphics card problem could be as easy as leaving the lower intake fan in front and installing an additional side fan as exhaust, but we had not ordered another fan.
There is a silver lining to this cloud, as AMD fans will get to see today’s system go clock-for-clock against the previous AMD-based build.
Familiarity might breed contempt in personal relationships, but it also compelling us to use MSI’s overclocking utility in spite of EVGA’s similar efforts. Based on RivaTuner, it’s free to users of any manufacturer’s cards.
The one thing that constantly pushes us towards MSI’s utility is its easily-configured fan map. This feature also removes the 70% fan limit we’ve seen when using Nvidia’s tuning software.
The frequencies stick at reboot, but the utility must be running for its fan map to work. We set it to start automatically at boot, minimized to the tray. Our final frequencies of 845 MHz core and GDDR5-4200 were determined after significant trial and error, which included the use of higher voltage levels that appeared somewhat unstable.