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Overclocking

System Builder Marathon, Q1 2014: The $2400 People’s Choice PC
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At 1.32 V CPU core, ASRock’s Turbo 4.60 GHz overclocking profile provided more than enough voltage to prevent crashing on this Core i7-4770K.

Unfortunately, that high voltage also caused it to throttle within seconds of starting an eight-thread run of AVX-optimized Prime95. Experimentation showed that a minimum of 1.275 V was needed to make this core run at 46 x 100 MHz, but that this voltage still caused thermal bottlenecking within minutes of my stability tests.

Some overclockers will point out that my stress test is unrealistically tough, that thermal throttling prevents damage, and that this protection mechanism takes minutes to start under Prime95. So, it'd be unlikely to affect our benchmarks. But when I look for a stable overclock, I avoid throttle conditions altogether. I instead dropped the CPU multiplier to 45x and began looking for the lowest voltage that would keep the CPU stable at 4.5 GHz.

A 1.24 V VCore worked great, so I also dropped the ASRock 4.60 GHz profile’s 1.30 V “CPU Cache” voltage to 1.24 V.

I increased the memory subsystem from its DDR3-1866 profile to DDR3-2133, and also configured it to 1.60 V.

To achieve stability at DDR3-2133, the three primary latencies all needed to be increased by one cycle beyond XMP settings. I usually find that tRAS can also be tightened, but that wasn’t true for this combination of memory and CPU.

As with the CPU, I don’t like the idea of graphics cards that throttle down when you need full power the most. I first increased the GPU power limit to its maximum slider setting, then began bumping up GPU clock in 25 MHz increments. After finding +175 MHz unstable and +150 MHz stable, I picked a frequency that would result in a nice round number for the GPU clock. Adding 157 MHz yielded a 1020 MHz GPU base clock and a 1059 MHz typical GPU Boost frequency.

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