Intel K Series Processors
Published: 7th June 2010 | Source: Intel | Price: £199 - £309 |
Test Setup and Overclocking
ASUS Maximus III Extreme P55
4GB Corsair Dominator (running at 10x)
Noctua NH-D14 with MX3
Windows 7 Ultimate
Intel i7-870, Intel i7-875K, Intel i5-655K
We also tested a i7-930 for comparison, using the above but with 6GB of Corsair Dominator and a Rampage 3 Extreme. Although the i5-655K comes with an integrated graphics chip, for ease of comparison and because the chip hasn't changed since we last tested it, we'll be skipping that part of the testing.
Stand by and hold on tight. 8 CPU-z coming up, but thankfully the text is brief because the overclocking is easy.
Stock shot on the left. As is normal with overclocking, heat is the main issue. However with the 655 following the 650 in being a 32nm chip this shouldn't be an issue and sure enough it proved not to be so. A full Prime95 run with the chip at 4.45GHz doesn't even crack the 57°C mark. Now we have a serious air-cooler in play here, but even a standard 120 type will run this chip at 4 to 4.4GHz all day without a problem. So we've got quite a lot of overhead to push on with.
Finding the highest stable speed we could run was simple as the even a complete neophyte to overclocking will be able to happily hit 4GHz thanks to the ease you can extract performance from this chip. With a rather hefty bit of voltage we managed to get 4.7GHz despite the extremely warm weather that England has experienced in the past week. Waiting until it got as cool as it's likely to we got just past 4.8GHz. A stunning overclock. We're convinced this chip can do 5GHz on air and would love to revisit this in the future.
As it is a 1.6GHz overclock which nobody could complain about. For our testing we're sticking with the 4.4GHz above to ensure stability.
Moving to the 875K, the results are somewhat less impressive. Although they would struggle to be as good as the 655K. Starting with the BCLK test we found 225MHz to be the limit, although the 1.36v needed to get to this small level is of some concern.
The BCLK only going to 225 was a bit of a sign of things to come, as the main problem with the 875K is getting it stable at an kind of decent BCLK. Rather most of the overclocking has to be done using the multiplier. Not being happy having to run over 1.4v as any kind of 24/7 overclock we knocked the multiplier down to 25 for a 4.28GHz overclock at 1.36v core.