Intel Core i7 875K Processor

Full Review

Intel’s new line of Core i7 / Core i5 / Core i3 processors have managed to fetch the desired result. You are now hard-pressed to see any new desktop or laptop launch that does not include this line of processors, despite the continuing availability of Intel’s older and lower-priced Core 2 Duo (C2D) and Core 2 Quad (C2Q) line-up. However, while the older C2D/C2Q line of processors for consumers were all based on the LGA775 socket, the newer line takes market segmentation very seriously indeed. Thus you have one socket type (LGA1366) for the high-end processors, and another type (socket LGA1156) for the mainstream. Even among LGA1156 processors, the ones with graphics built-in (like the Core i5 661) form yet another line of their own by demanding a different motherboard chipset.

This processor is the best you can buy for a mainstream P55-based system, but it targets an extremely tiny niche of the market.

The launch of the Intel Core i7 875K processor solves some of these gripes. The Core i7 875K is essentially the same as a Core i7 870 processor, except that the multiplier of the 875K is unlocked, which helps overclockers. This processor uses the LGA1156 socket, which is supported by any mainstream desktop motherboard that employs the Intel P55/Q55/H55 chipset. The Core i7 870 sells for Rs. 18,000 in India, while the Core i7 875K will sell for Rs. 22,000. The unlocked multiplier makes for the difference of Rs. 4,000 in price, a premium that might be gladly paid by the niche audience it targets. Until now, the only processors with an unlocked multiplier were the higher-end Core i7 processors that use the LGA1366 socket and the high-priced X58 chipset on the motherboard side, a combination that could easily cost three times the price of the 875K processor. The price of the 875K may not fall by much considering its niche, once it has outlived its utility and pricing-segment, Intel might just find it easier to pull the plug on its sales.

Features and Specifications
The Core i7 875K is a quad-core manufactured on a 45nm fabrication process. It is rated at a TDP of 95W (power consumption of 95 Watts on average). It is similar to its Lynnfield series sibling (i7 870) which is based on the Nehalem architecture, in almost every way. If you have been reading our motherboard reviews, you’d have observed that the Intel Core i7 870 processor had tremendous headroom, and it overclocks by a whole Gigahertz without breaking into a sweat. Thus Intel offered this variant of the same, to make over-clocking easier and you probably want this to achieve a more stable over-clock.

By default, the 875K runs at a clock frequency of 2.93 GHz with a TurboBoost speed of 3.6 GHz. When the processor is being under-utilized by the OS/software, TurboBoost kicks in by disabling half the number of cores to run the processor at a higher speed. This benefits software that is not multi-core aware and is hungry for raw Megahertz power. HyperThreading whereby each core simultaneously runs two threads, is also present. Thus the 875K presents itself to the operating system as being capable of running 8 threads simultaneously on its 4 cores.

Performance
To prevent bottlenecks and to compare the scores to the normal i7-870 processor, we tested the Intel Core i7 870K processor on a test rig comprising of the following components – an Intel P55 motherboard, ThermalTake heatsink and cooler, 2 GB of Kingston DDR3-2000MHz RAM in dual-channel mode, Radeon 4870X2 graphics card, Intel X25-M 80GB SSD, Tagan BZ-1300W PSU and Windows 7 Ultimate Edition.

We ran the first round of tests at default clock speeds. Storage input/output, USB, RAM and processor cache speeds were on par with the i7-870. On PC World’s own WorldBench 6 benchmark suite, we saw a score of 129. On CineBench, we saw a CPU benchmark of 14,264 CB. On PC Mark 05 and PC Mark Vantage we saw a score of 13,993 marks and 12,361 marks respectively. In the “Performance” pre-set of 3D Mark Vantage, the 875K garnered a CPU score of 19,014. Among games, Crysis gave 58 fps (frames per second) at a resolution of 1024x768 with Ultra High graphics and anti-aliasing disabled. All of these are good numbers and this is the best performance that can be achieved on an LGA1156 processor at stock speeds (pre-OC). You can view the results of Far Cry 2, more synthetic benchmarks and real-world tests conducted at stock speeds on the “Performance” tab of this review.

Over Clocking
In stress tests that we conducted, its maximum temperature at load increased from 35 °Celsius at default speed to 45 °C when overclocked in a temperature-controlled AC room. We managed to reach a stable overclock of 4.18 GHz on normal air cooling by using a combination of increased multiplier and FSB. Since the multiplier of the 875K is not locked, there is no upper limit and you can reach the upper limits of what your motherboard supports. We could up the multiplier from 22x to 30x (the maximum on our motherboard) to get to 3990 MHz even before touching the FSB or memory speeds, so this could be called the “safe limit”. Of course, to extract the last bit of performance we had to lower the multiplier and memory speed a bit, to be able to increase the FSB (Front Side Bus, 133MHz by default). Going beyond 4.18 GHz required us to have lower-voltage memory and liquid-cooling, but it is quite conceivable to have obtained higher clock speeds from this processor. It is worth keeping in mind that over-clocking is like running your system out of line with manufacturer specifications, so wear and tear could increase. Power consumption of the processor could rise by as much as 70 per cent, which does take a toll on your power bill. In benchmarks, rendering applications and games, we saw performance improvements that ranged between 15 to 25 per cent after overclocking the Intel 875K by 1.25 GHz – from 2.93 GHz to 4.18 GHz. This would indicate there could be other bottlenecks in the picture (graphics card) and that there is room for software to scale better, since they did not manage to use 100% of all threads/cores of the CPU. Thus the increased power consumption, risk of killing system components, and price of getting higher-quality components may not be worth the performance improvement for everyone.

This processor is the best you can buy for a mainstream P55-based system, but it targets an extremely tiny niche of the market. Most normal buyers would choose a far cheaper processor. Desktop enthusiasts who want to toy with their hardware and extract every last ounce of performance and actually own such high-end components for the other parts of a PC, are likely to choose an LGA1366 (X58 motherboard) solution instead. That leaves just reviewers like me who test socket LGA1156 motherboards, and the few people who own sufficiently-good PC internals to OC that high, who baulk at the price of a multiplier-unlocked LGA1366 mobo+processor combination. They would like a temporary solution that can do what they need, while they put together a higher budget to buy Intel’s top-end LGA1366 unlocked processor. That audience may indeed be sandwiched between two much more visible market segments, but we have to give the thumbs-up to Intel for realizing the demand and catering to even that tiny niche.

Bottom Line

The Intel Core i7 875K is the fastest processor for mainstream desktop computers. This socket LGA1156 processor is compatible with P55/H55/Q55 chipsets, with specifications identical to the quad-core Core i7 870. The unlocked multiplier differentiates it and makes it the best choice for overclockers, albeit at a price premium.
It is priced higher than even the mid-range Core i7 930 processor (LGA1366), which places the 875K in a very tiny niche - this lops off some points from its PCW Rating.