What happens when you inject a processor with botox? Something not unlike this speedy new processor from Intel...
Though we're not always ones to toot our own vuvuzelas, we were rather hyperbolic in our initial review of the i7 870 back in Issue 105 - but there is always something better just around the corner, and that corner has just been passed. Or has it? Intel's newest processor certainly appears to be very similar to the earlier model, and it seems the similarity isn't only skin deep.
The 875K sits in a fantastic place in the market and actually undercuts the preceding model by over $200. It misses out on the inclusion of a stock cooler, though proper enthusiasts wouldn't bother with such a wimpy hunk of metal and would (we hope) usually opt for aftermarket cooling no matter the build.
Specifications of the chip are identical to the 870 across most major points: the 875K has four 32KB L1 caches, four 256KB L2 caches, and a large shared 8MB cache that can be divided up by the cores on a situational basis - memory-hungry workloads can demand more, while lighter loads can use less. It retains the 95W power envelope and the 45nm manufacturing process, as well as the LGA1156 socket, and also sits at the same stock speed of 2.93GHz. In fact the 875K is so similar to the 870 that you'd almost certainly be hard-pressed to notice the difference!
A difference there must be, however, and in this case it is highlighted by the 'K' moniker attached to the name. This indicates that the processor multiplier is not locked as with most others. The locked multiplier is similar to a teacher keeping track of a class under exam conditions - and unlocking the multiplier produces the same result as removing the teacher in the same circumstance, allowing the students to cheat without restriction. By cheating we of course mean overclocking, and with the ability to change the base multiplier of the processor independently of the motherboard comes some new freedoms.
Traditionally, overclocking a processor involves raising the working frequency of the motherboard whose frequency is the value the multiplier relies upon to get the final processor speed, in this case 22x133, and therefore the stresses are placed on the system as a whole. Rather than raising the frequency, an unlocked multiplier can be raised independently without affecting other components to the same degree - and with this method we achieved a maximum stable overclock of 4.26GHz using a 32x multiplier and the same operating frequency of 133MHz, albeit at a higher core voltage of 1.424v. Impressively we even managed to get the system booting at 33x133, which equated to 4.39GHz and returned a wPrime score of 5.864 seconds - though this was not stable enough to run Cinebench.
Performance of the 875K at stock settings was identical to the 870, though our sample seemed more enthusiastic about raising its frequency with Turbo Boost to give a few extra points in benchmarks. Four processing cores can certainly chew through workloads quickly, and hyperthreading is put to good use to generate some decent efficiency changes when moving from single-threaded applications to multi-threaded ones.
Ultimately the 875K is a greatly affordable enthusiast processor that offers a lot of flexibility when overclocking, though probably isn't worth upgrading to if you've already got a Core i7 processor.
Trusted execution technologyIntel has skimped on one feature of the 870, and 'trusted execution' can roughly boil down to hardware antivirus protection - only allowing software to run in enclosed bubbles called 'measured launched environments' that keep nasties away from essential cogs in the operating system. As this was rarely used, it's a feature that won't particularly be missed, but it's nice to know where things were removed.
Issue: 133 | February, 2012