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Intel's Core i7-875K and i5-655K processors

The K is special

In CPUs, it's good to be king, because the king gets to decide things. If you're not king, you may be able to get away with all sorts of shenanigans, but you ultimately serve at the king's pleasure.

Take, for instance, AMD's recent resurgence in desktop processors. Although Intel has held the overall performance crown in an unbroken run since the introduction of the first Core 2 Duo, AMD has been able to stay on the radar of PC enthusiasts through cunning and guile. When it had no hope of catching up to the fastest Intel chip in a given price range, AMD cooked up its Black Edition processors that removed clock speed caps and made overclocking dead simple—without the huge price premium traditionally commanded by Extreme Edition and FX processors. Even though Intel's CPUs were more attractive by most conventional standards, folks wanting value and performance suddenly had to weigh another variable. When it couldn't keep pace with Intel's quad-core processors using four cores of its own, AMD uncorked the Phenom II X6 and priced it directly opposite Intel's Lynnfield quads. You were quite literally getting more chip for your money from AMD, and the X6's strong value proposition was enough to earn it positive reviews.

Smart strategy will only take you so far, though, when you're not the king. Intel's chips extract more computational throughput from a smaller silicon area while consuming less power. From manufacturing to design and architecture, it has every advantage. Intel is king. As a result, Intel gets to decide how much performance it will deliver to customers and at what price. And now it appears, the king is a little miffed—cheesed, peeved, horked off, if you will—about the Phenom II X6's critical success.

Thus, the king has lifted his hand from the armrest of the throne and made a quick flourish—perhaps a slicing motion across the throat—and tilted his head in the general direction of the Phenom II X6. A little fiddling in the royal factories and a few marketing slides later, and the king's official response rides forth across the drawbridge, the Core i7-875K and the Core i5-655K. Both of the K-series CPUs are priced attractively and have unlocked core and memory multipliers for easy overclocking. And they offer precious little room for those pesky Phenom IIs to breathe.

Make way for the K series
Neither of the K-series processors is new speed grade from Intel. The Core i5-655K is just an unlocked version of the Core i5-650, and the Core i5-875K is an unlocked Core i7-870. The K-series parts have the same core clock, Turbo frequencies, and thermal envelopes as their unlocked brethren. What makes them different is the ability to crank up and down the core and memory multipliers at will. Well, there's one more major bit of news for the i7-875K, best illustrated by a look at how it fits into Intel's lineup.

Model Cores Threads Base core
clock speed
Peak Turbo
clock speed
L3 cache
TDP Price
Core i5-650 2 4 3.2 GHz 3.46 GHz 4 MB 2 73W $176
Core i5-655K 2 4 3.2 GHz 3.46 GHz 4 MB 2 73W $216
Core i5-661 2 4 3.33 GHz 3.6 GHz 4 MB 2 87W $196
Core i5-670 2 4 3.46 GHz 3.73 GHz 4 MB 2 73W $284
Core i5-680 2 4 3.6 GHz 3.86 GHz 4 MB 2 73W $294
Core i5-750 4 4 2.66 GHz 3.20 GHz 8 MB 2 95W $196
Core i7-860 4 8 2.80 GHz 3.46 GHz 8 MB 2 95W $284
Core i7-870 4 8 2.93 GHz 3.60 GHz 8 MB 2 95W $562
Core i7-875K 4 8 2.93 GHz 3.60 GHz 8 MB 2 95W $342

Intel charges a bit of a premium for the 655K versus the 650, but the 875K is $220 cheaper than the Core i7-870—at least right now. One would expect the Core i7-870's price to snap into line or the product to be canceled, but Intel says it has no plans to change the i7-870's price "in the near term." So it may just hang around as a singularly poor value. Whatever happens, the 875K gives you a more flexible CPU for a whole lot less cash.

In fact, the i7-875K costs roughly 50 bucks more than the Phenom II X6 1090T Black Edition, AMD's fastest desktop processor, which is also unlocked. No doubt Intel charges a little more because, at stock speeds, the Core i7-875K is faster than the X6 1090T. We know this because the Core i7-870, with the same stock clocks, was faster overall in our review of the 1090T. Still, the price is close enough that 875K's intended target is pretty clear.

The Core i5-655K isn't such an obviously good value. At $216, it slots into the existing price structure for Clarkdale-based dual-cores, and we've long thought Intel charges too steep a premium for the higher clock speeds of those CPUs. Heck, the 655K costs more than the Core i5-661, which has higher stock clocks for both the CPU cores and the integrated graphics, so there's a premium for the unlocking, too. If you leave overclocking out of the equation, we'd prefer Intel's $199 quad, the Core i5-750. The closest competition from AMD has more cores, as well: the Phenom II X4 965 Black Edition is $185, and the Phenom II X6 1090T is $199.

Then again, you can't really leave overclocking out of the conversation when you're talking about a 32-nm Clarkdale processor, for reasons we'll make clear shortly.