In these videos we are going to show how to overclock a socket AM3 Phenom II X4 955 Black Edition CPU. We will take this CPU from it’s stock speed of 3.2GHz and will gradually increase it’s speed all the way up to 3.8GHz. This process works for any Phenom II based CPU. This includes Phenom II and Athlon II CPUs. You will see every step along the way so you can apply the same process and maximize your computer’s performance.
Before we get into how to overclock a Phenom II based CPU we need to understand some basics of how a CPU’s speed is determined.
Frequencies and Multipliers
When you see that a Phenom II X4 955 Black Edition CPU runs at 3.2GHz, that speed is derived from a reference frequency, also referred to as the Reference Clock, or ref. clk, times a multiplier. All Phenom II CPUs have a standard reference clock of 200MHz. In the case of the Phenom II X4 Black Edition the multiplier is 16x. If you multiply 200×16 you get 3200 or 3.2GHz. Here is a list of all the current Phenom II and Athlon II based CPUs with their standard reference clock and multiplier at stock speeds. You can find a complete list of ref clk and multipliers for all Phenom II based CPUs here http://en.wikipedia.org/wiki/List_of_AMD_Phenom_microprocessors
To overclock the CPU we have to increase either the ref. clk or the multiplier. With the exception of the Black Edition CPUs, also shown as BE in the model number, all other Phenom II based CPUs can not increase their multipliers beyond the stock setting. You can lower the multiplier, but increasing beyond the stock settings is not possible.
The Black Edition CPUs have an unlocked multiplier which means it can be increased beyond it’s stock setting. Leaving the ref clock at standard you can simply increase the multiplier to increase the speed the CPU runs at. This is the easiest way to overclock a CPU, but since the smallest increase of the multiplier is .5, the smallest increase is .1GHz. To find the absolute highest overclock your CPU is capable of you can also increase the ref clk, 1MHz at a time to fine tune the overclock.
In addition to using a combination of ref clk and multiplier increases to overclock the CPU we will also show how to overclock the CPU using only ref clk increases. If you have a non Black Edition CPU this is how you will be overclocking your CPU because the multiplier is locked, meaning it can be lowered, but not raised beyond it’s stock setting.
The ref clk also effects three other frequencies. These are the HyperTransport Link, or HT Link, CPU North bridge of CPU NB, and memory frequencies. The HT Link is what connects the CPU to the rest of the motherboard. The CPU NB 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 ref clk to find the maximum CPU frequency, we will also 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 HT Link, CPU NB and memory frequencies stay within their limits.
Voltages and Temperatures
As we individually raising the frequency of the CPU, CPU NB, HT Link and memory they will eventually reach a point where one or more components become unstable. To combat this instability, we will increase the voltage to the components as needed. The increased voltage will help stabilize the components.
There are three voltage settings we can change to help improve the stability of an overclock. These are the CPU VID or Voltage Identification Digital, which is the voltage going to the CPU cores themselves, the CPU NB VID or Voltage Identification Digital, which is for the CPU cache and the memory controller on the CPU and the DRAM Voltage which is the voltage going to the memory.
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 it’s cooling.
One of the most important rules about overclocking is that you don’t want to try to overclock more than one components at a time. For instance if we tried overclocking the CPU and RAM at the same time and the system became unstable we wouldn’t have any way to tell if it was the CPU or the RAM that caused the instability.
What we’re going to do is use a combination of ref clk and multiplier settings to overclock one component at a time while keeping the other components at or below their stock speeds. This will insure that there is only one possible cause of instability.
Once we have found the CPU’s maximum frequency will will use it’s multiplier to lower the CPU speed so it is at or below it’s stock setting. We then find the maximum speed of the CPU Northbridge and HTLink using ref clk and multiplier settings making sure we keep the other components at or below their stock speed to prevent them from causing instability.
We will use this isolation process on the memory to find it’s maximum speed.
Once we have each component’s maximum stable frequency we will combine the overclocks so that all of the components are at their maximum stable speeds.
With all of these settings it is easy to forget what changes you make, what worked and what didn’t. It’s extremely important to keep notes while you overclock. For each new overclock attempt you need to write down all of the settings used for that overclock. We are going to be making a lot of settings changes. If we don’t keep track, it will become overwhelming.
In the next lesson will be run some tests on our CPU with stock settings to get a baseline for how well it is being cooled and performing.