Core i7-3820 Overclocking
Although a few paragraphs earlier we complained about the limitations for the Core i7-3820 clock frequency multiplier increase, which can be set at 43x maximum, the new clocking algorithm for CPU, bus and controller frequencies implemented in the LGA 2011 platform may, in fact, help. Due to the use of an additional co-multiplier for the CPU frequency, the base BCLK frequency may be set not only to 100, but also to 125 or 166 MHz (give or take a few megahertz) without any stability issues. However, not all processors will work with the 166 MHz BCLK, the 125 MHz setting is a 100%-operational option, which will make it possible to successfully overclock Core i7-3820, even though it doesn’t belong to the overclocker CPU series.
In other words, the maximum Core i7-3820 frequency you can reach during overclocking by raising the processor clock multiplier at the default BCLK frequency will be only 4.3 GHz.
Note that Turbo technology remains partially operational in this case, and in case of low CPU utilization its frequency may automatically increase to 4.4 GHz.
However, if you set the BCLK frequency at 125 MHz, you can theoretically hit as high as 5.3 GHz. Of course, in reality you can only get that far if you are using extreme cooling methods. We, however, stuck to air cooling, NZXT Havik 140, and managed to use 37x multiplier to overclock our Core i7-3820 to 4.63 GHz without losing stability.
If we set the multiplier to 38x, we couldn’t get the system to stabilize, but we could slightly improve our maximum result by raising the BCLK frequency to 127 MHz. We ended up with 4.7 GHz clock speed.
To prevent stability losses under heavy load, we had to increase the CPU Vcore to 1.45 V, but the CPU thermal mode in this case remained quite acceptable: the temperature didn’t exceed 80°C. So, there was no sight of any throttling, which in Core i7-3820 processors, unlike other LGA 2011 CPUs, occurs at 100°C.
Unfortunately, 4.7 GHz is not a remarkable achievement for 32 nm Intel processors. Quad-core Core i7 processors for LGA 1155 platform overclock at least just as good, which makes Core i7-3820 a decent, but not the best choice for an overclocked system. And that is quite easy to explain. Sandy Bridge-E semiconductor die that is used in LGA 2011 processors is much more complex, but is manufactured using the same 32 nm process. So, the frequency potential of Core i7-2700K and Core i7-2600K simply has to be higher by definition.