Intel’s Core i5-655K & Core i7-875K: Overclocked and Analyzed

Ok, so we got a little carried away on the Clarkdale stuff. Time to give the i7-875K a look-see. After all, it’s probably the bigger story of the K-series release given it offers more overclocking features and a similar stock clock speed to the more expensive i7-870.

No beating around on this one, we started off with watercooling:

Things are fine up to 3.7GHz, but any higher and things soon get out of hand. CPUs like these are fine if you need a stock runner, or are looking for a basic overclock, although this kind of performance is easily available from the cheaper i7-860.

 

Without water-cooling, there isn’t much headroom at all - at least not on this sample. Our i7-870 ES manages 4.4GHz, pulling 201 Watts during Linpack. The 875-K is already at 193 watts, and it has barely broken 4GHz.  Past 3.9GHz, we’re already looking at a 10W increase in power consumption for every 20 MHz rise in CPU frequency - let’s just say that this did not encourage us to push any further. Well, that’s not completely true because we did try it out under our cascades. Unfortunately, things are pretty bad in the sub-zero realms, too. The substrate can’t handle more than 1.35Vcore when cooled below -70 Celsius, making it a difficult chip to control and one that’s ultimately limited in headroom. The best we managed was a run of Vantage at 4.5GHz, which really isn’t worth bragging about.