In these videos we are going to show how to overclock a socket 1366, Core i7 920 CPU. We will take this CPU from it’s stock speed of 2.66GHz first up to 3.2GHz and will gradually increase its speed all the way up to 4GHz. You will see every step along the way so you can apply the same process to your Core i5 or Core i7 CPU and maximize your computer’s performance.
Before we get into how to overclock a Core i5 or i7 CPU we need to understand some basics of how a CPU’s speed is determined.
Frequencies and Multipliers
When you see that a Core i7 920 CPU runs at 2.66GHz, that speed is derived from a base frequency, also referred to as the Base Clock, or BCLK times a multiplier. All Core i5 and Core i7 CPUs have a standard base clock of 133MHz. In the case of the Core i7 920 the multiplier is 20x. If you multiply 133×20 you get 2660 or 2.66GHz.
To overclock the CPU we have to increase either the BCLK or the multiplier. With the exception of the Core i7 975, all other Core i5 and Core i7 CPUs can not increase their multipliers beyond the stock setting. You can lower the multiplier, but increasing beyond the stock settings is not possible, except in the case of using Turbo mode which we will talk about later.
The Core i7 975 has a unlocked multiplier which means it can be increased beyond its stock setting. Leaving the base clock at standard you can simply increase the multiplier to find the maximum overclock the CPU can handle. This is the easiest Core i7 to overclock, but it’s also the most expensive at $1000. What we’re going to do is take the cheapest socket 1366, Core i7, the 920 and show you how to overclock it by increasing the base clock. We will make it faster than the 975 for $700 less. Again, these methods will work with all Core i5 and Core i7 CPUs.
The base clock also effects three other frequencies. These are the Quick Path Interface or QPI, the uncore, and memory frequencies. The QPI is what connects the CPU to the rest of the motherboard. The uncore is everything on the CPU that is not the CPU cores. This includes the cache on the CPU and the memory controller on the CPU. The memory frequency is just what it sounds like. It’s the frequency the memory runs at. Typically this is 1066, 1333, or 1600MHz.
By increasing the base clock, we will be increasing the frequency of these other components. This could result in overclocking these components to the point where they cause the system to be unstable before the CPU can reach its’ maximum overclock. Fortunately, each of these components have their own multiplier that we can set. We will lower these multipliers so the QPI, uncore and memory frequencies stay within their limits to keep the overclock of the CPU stable.
Voltages and Temperatures
When raising the frequency of the CPU cores, QPI, uncore and memory we will eventually reach a point where one or more components become unstable. To combat this instability, we will increase the voltage to one or more of the components. The increased voltage will help stabilize the component.
There are four voltage settings we can change to help improve the stability of the overclock. These are the Processor core voltage, which is the voltage going to the CPU cores themselves, the uncore voltage, which is for the QPI and CPU cache, the memory voltage which is the voltage going to the memory itself and the CPU Phase locked Loop or PLL which is a control system for the CPU.
By raising the frequencies and voltages we will also raise the temperature inside the CPU. Depending on the cooling you have for your case and CPU as well as the ambient room temperature, at some point the increased heat may be too much for the CPU to handle. To push the CPU further we would first need to improve its cooling.
In the next lesson we will run some tests on our CPU with stock settings to get a baseline for how well it is being cooled and performing.