The way traditional overclock processors in LGA775 is through the FSB frequency, which determines not only the frequency of the processor but also the memory and other peripherals. In the current plates, the frequency of memory can be adjusted independently, allowing (in the supported by the modules) to increase the frequency of memory in order to gain some additional points, or reduce the frequency of memory in relation to the FSB, allowing the clock of the processor increases, but the memory still operating on a frequency close to the original.

Core I7 in the process changed a little, since it uses no more the FSB. In his place, a base frequency (Host Clock Frequency), named BCLK (which in early models of the Core I7 is 133 MHz) from which are obtained from 4 different frequencies:

a) The frequency of the processor cores, which as in previous ones, is achieved through a multiplier, which goes from 20x in the I7-920 to 25x in I7-965 XE. The multiplier is unlocked in the series XE models (one purposeful spread to justify the difference in cost) and blocked in the other processors.

b) The frequency of the memory controller, L3 cache and other components ancillary to the embedded processor, which are collectively called uncore. The nominal frequency is 2:13 GHz for I7-920, 940 and I7-I7-950 (multiplier of 16x) and 2.66 GHz for the I7 and I7 XE-965 XE-965 (20x multiplier). The basic rule is that the frequency must be at least twice the frequency of memory.

The frequency of uncore is the second most important factor for the performance, losing only to the clock of the nuclei. The reason is simple: the clock of uncore determines the frequency of operation of the L3 cache, which is a fundamental factor to the performance of the I7.

By increasing the frequency of uncore from 2:13 to 2.66 GHz, the latency of L3 cache is reduced from 41 to 36 cycles, a gain of 12%. A large percentage of the difference in performance between the I7 and I7-950 XE-975 is just the difference in the clock uncore.

c) The frequency of QPI bus (which connects the processor to the chipset), which is 2.4 GHz in the I7-920, 940 and I7-I7-950 (multiplier of 18x) and 3.2 GHz in I7 and I7-965 XE-965 XE (24x multiplier). Depending on the motherboard, the Setup can report the frequency of QPI directly, or inform the actual frequency (in MT / s), which corresponds to the frequency multiplied by 2.

d) The frequency of DDR3 memory modules, which is 1066 MHz (8x multiplier) in the regular models and 1333 MHz (10x multiplier) in the XE series. The frequency of memory increases with the frequency basis, but it is possible to reduce the multiplier, not to exceed the frequency supported by the modules.

With the exception of the XE series of processors, the multiplier is locked in memory for more, so it is not possible to increase the frequency of the memory without increasing the frequency from baseline.

Both the uncore as the QPI offer a good tolerance to higher frequencies as the uncore operates at a frequency lower than the rest of the QPI processor and is designed to work at 3.2 GHz (frequency that is used in the XE series of processors) . As a result, the main concerns when you overclock just as the frequency of cores and memory, not very different from what we have in a Core 2 Duo

BCLK to increase to 166 MHz in the I7-920, for example, the cores will work to 3.33 GHz, 2.66 GHz to the uncore, memory to 1:33 GHz to 3.0 GHz and QPI, a configuration that should work without problems if you are using a good cooler and the 1333 MHz DDR3 modules or more.

When you try to go further, you will eventually encounter instability related to the processor (which is often caused skin itself, or increase in temperature), in memory, or possibly related to the L3 cache or other components of the uncore . We come then to the issue of tensions.

The default voltage of the models of 45 nanometers of I7 is 1.2V, you can increase tension with some security for up to 1.35V. The major problem in increasing the frequency of the processor is that the heat dissipation increases proportionally, which makes it necessary to use a cooler more efficient (that is why firms like noctua coolers earn as much money selling high-performance). If the problem is the temperature, increasing the tension ends up being counter-productive.

Although the best performance use the Intel processor in various tasks to justify the higher consumption, the fact is that I7 is a slightly more extravagant as the Core 2 Quad based in Penryn, which makes the cooler and ventilation of the cabinet factors especially important when you overclock.

Then we have the tension of uncore, which also is 1.2V and can be safely increased up to 1.35V. The tensions of the processor and the uncore are independent, so you can just increase the uncore (not significantly raises the consumption of the processor) or vice versa.

Increasing the tension of the uncore is usually necessary to increase the base frequency to 175 MHz or more, point where the memory controller begins to show signs of fatigue.

In conclusion, we have the function of memory, which is still performing the same function as the LGA775 boards, allowing the memory modules support voltages higher. Although many manufacturers produce memory kits with rated voltages of 2.0V or even more, Intel recommends using no more than 1.65V, warning that higher voltages can cause damage to the integrated memory controller of the processor.

Despite the use of CMOS and other techniques to reduce the I7 offers a good potential for overclocking, even with the I7-920 at 3.4 GHz (BCLK of 170 MHz) without much difficulty.Increasing tensions and using a high performance cooler can reach 4.0 GHz in most cases, but at this point the thermal dissipation begins to exceed what is feasible using the cooling air. As always, you can go a little further using a watt-cooler, but the cost has not recovered.

As always, the quality of waffers and hence the maximum frequency of operation of the processors in overclock, tends to increase as production increases and Intel perfects the technique of production. It should not take up that new series of processors are able to reach the mark of 4.5 GHz

Anyway, any more aggressive overclock, it is important to disable the Turbo Boost, since the increase of 266 MHz is just enough to destabilize the processor. Look for the "Intel Turbo Mode Tech" or "Enable Turbo Boost".

Another important option is the "CPU VR Current Limit Override" or "CPU TM Function", which controls the behavior of the PCU controller embedded in the processor. By default, it reduces the frequency of the processor where the TDP or the maximum amperage is reached, limiting the very frequencies that you can achieve the overclock. To remove the obstacle, you must disable the function.

For XE series of processors, things are a little easier, because the multiplier is unlocked, allowing you to increase the frequency of the processor without having to touch base frequency. For processors are selected within the production line, they are also able to achieve slightly higher frequencies than the cheaper models, but the difference in price means that they are not a good idea.

As in other cases, the best cost-benefit is to use the I7-920, which is the cheapest model of the line (or possibly the I7-940, when it dropped in price) and combine it with a good and the motherboard a good cooler, offsetting the additional expense with a good overclock.