Overclocking Core i7 875K

Overclocking Core i7 875K

For the Lynnfield core based product we have chosen the exact same motherboard. eVGA's P55 is quite a delicious board to overclock on. Tweaking is fun with this quad-core processor. Just play around with CPU voltage, BCLK and multiplier. I guarantee you that even on the stock air cooler you can achieve some pretty interesting results. Your voltage sweet spot will be 1.35 ~ 1.40 Volts for the 4 GHz processor clock area. We were able to overclock the Core i7 875K processor to 4.2 GHz on a regular heatpipe based cooler.

But let's get started. First up, check what your current values are. For example, say the Intel P55 mainboard applies a dynamic multiplier that would be a maximum of 133x22, which is ~ 2.9 GHz for the 870 and this 875K.
Don't be afraid to play a little, and if the system crashes... heck whatever, that's part of the experience my man. You seek the maximum. If you hate that kind of stuff, well, then this processor and overclock experience is not something you want to pursue anyway.

We were hoping to get the processor a little higher, but the processor got close to 4.2 GHz on all four active cores with a heatpipe based air cooler. Here's what we did:

• Enable Turbo mode
• See a good processor multiplier (26)
• Increase processor voltage a little bit to 1.375v
• Lower QPI ratio (as close as possible to 2400)
• Lower memory multiplier to maximum stable memory frequency
• Increase CPU base frequency (160 MHz)

At 4000 MHz on the air cooler we easily booted into Windows. We settled at 26x160 @ 1.35 Volts. The end result was a stable 4169 MHz.

When we stress the CPU cores with Prime 95, temperatures now rise to 84 degrees C (183F) which really is the maximum limit you want to go to. But... 4.2 GHz air cooled is just downright good and falls within what we feel this processor needs to be capable of.

Overclocking itself is a pretty easy thing to achieve with this processor. Mind you that overclocking will draw much power from your system. Anyway, if you like to go higher then another cooling solution like LCS really is needed and recommended.