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Intel K Spec Core i7 875 and Core i5 655 Review

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The only way to know how a processor performs is to run it through a series of benchmarks, using both synthetic and real tasks to make a comparison as to how the processor performs against architectures from the same manufacturer, as well as competing manufacturers. Obviously, this leaves Intel and AMD at this point. To test these unlocked processors, all of the energy saving features as well as performance boosting technologies have been disabled on the motherboard in order to gain repeatable results. Otherwise, the results would not be a valid form of comparison. Intel's Turbo Boost technology provides a serious clock increase on this CPU that allows it to deliver performance in excess of what is available when the technology is disabled. A comparison will be made against both AMD processors and both the Intel socket 1366 and socket 1156 processors. Once the stock testing is completed, I will overclock the Core i7 875 and Core i5 655 to see if they deliver any overclocking headroom. Both stock and overclocked testing will be accomplished on the test platforms listed below.



Testing Setup: Intel Core i5/i7 Socket 1156


Testing Setup: Intel Core i7 Socket 1366


Testing Setup: Intel Core i5 Clarksdale Socket 1156


Testing Setup AMD Six Core:


Testing Setup AMD Six Core:


Comparison CPUs:



Overclocked settings:

  • Processor: Intel Core I5 655 4461MHz 159x28
  • Processor: Intel Core i7 875 4392MHz 151x29

The reason that these two processors exist is the flexibility of overclocking with the multiplier. Hence, that's the path I took with the testing of this pair of processors from Intel. Both chips would pull in excess of 4.6GHz for screen shots but screen shots are just that. Reliable overclocks are what I was after. Along that vein, I pushed the multiplier first to find the maximum clock speed I could run with each chip. For each one the limit really depended on how much juice I wanted to supply to that piece of silicon under the heatsink. Running the base clock at 133MHz, each chip would move well into the 30 plus range on the clock multiplier before running out of steam. Reaching the limits at around 4.5Ghz for stability with reasonable voltages on each chip, I knocked the multiplier back down and started giving the bclock an increase to really drill down the maximum, prime-stable clock speeds. The best combination of bclock and multiplier for the i5 655 was 159x28 for a final speed of 4461MHz. The 875 was a little more stubborn in this respect at 151x29 and 4392MHz. These numbers are a bit better than the 870 and about the same as I can get on the i5 661. But to do it with those chips requires you to tweak all the voltages to get there. While with the ability to work on multiplier alone, you really do not have to wring the screws off when adjusting voltages. This I feel is a good compromise for the majority of users. You can still spin the bclock to +200MHz, but with these chips you don't have to.



Intels Turbo Boost technology allow the processor to run at a higher frequency by dynamically increasing the clock speed to a higher level with no input form the user. This is done automatically as long as the BIOS is configured correctly. The maximum Turbo Boost frequency for these processors is 3.46 GHz on the i5 655 and 3.6Ghz on the i7 875. In my testing I saw maximums not quite this high and running in the 3.3+Ghz range. With these CPUs I found a nice little bonus in the BIOS. You can manually set the maximum Turbo Boost multiplier manually so that the actual boost will be more pronounced. But like anything else when pushing the limits, you need to test stability to verify that you can run the speeds you want.


Maximum Clock Speeds:

Each CPU has been tested for stability at the clock speeds listed when in an overclocked state. These clock speeds will represent the overclocked scores in the testing.




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