Intel Core i7 920 2.66GHz Nehalem Processor

Test System

CPU-Z and Speeds

Looking at the main CPU-Z tab, one can notice some interesting things about this particular processor. Firstly I would like you to note the “Specification” field. This field reads “Genuine Intel(R) CPU 000 @ 2.67 GHz (ES)”. The most important part of this statement is the “ES” part. This signifies that our particular model is an engineering sample and has limited capabilities. The capability limit comes in the form of a locked ram multiplier. In prior processor designs, RAM speeds were mostly determined by the FSB (Front Side Bus) speed and either a locked multiplier, or an unlocked setting in which the user had the ability to set the RAM speed as he/she saw fit. Since the Core i7 system does not have a north bridge, FSB is nonexistent. The speed of the RAM then is determined by the base frequency of the processor and a RAM multiplier. When a stick of RAM is inserted with speeds higher than 1066 MHz, the multiplier kicks in so that the base frequency of the processor does not have to be increased in order to attain the higher speeds. What Intel had done with the engineering sample is lock that multiplier. This brings us to an important topic and also a disclosure statement. The processor was tested under the “Auto” conditions unless otherwise stated. This means that the Corsair Dominator 1600 MHz RAM was running at default speeds of 1066 MHz. We have also tried overclocking the system by turning up the base frequency up to 200 MHz and lowering the CPU multiplier to 14. This gave us a RAM speed of 1600 MHz and processor speed of 2.8 GHz, however the system became somewhat unstable and would randomly crash under heavy loads. Aside from this little nuance the processor ran more or less smoothly.

Overclocking

Overclocking with the Core i7 was different from how it used to be with the previous generation processors. Since there is no more front side bus, one has to adjust the base frequency of the processor. This frequency then gets multiplied by the standard multiplier. In our case the multiplier is maxed at 20. The standard frequency of 133 MHz gets multiplied by 20 thus giving us the rated speed of 2.66 GHz. The only problem is the memory. Since the processor clock is directly tied into the memory upping the memory in and engineering sample basically results in an overclock. Without the multiplier, we were not sure if the ram would have been able to cope with the overclock. We nonetheless decided to try and succeeded at 4.0 GHz overclock. Unfortunately it was not stable enough for benchmarking.

The i7 also has an automatic overclocking feature called Turbo Mode. This allows the chip to dynamically redirect power from unused cores and overclock the remaining cores (up to an additional 266 MHz) to increase performance in single threaded tasks. This feature only goes into effect if the chip is below its thermal threshold.

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