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Phenom II X6 Overclocking HowTo

In fact, the algorithm for overclocking or increasing the processor clock frequency above the nominal value for the purpose of boosting its performance is similar for all processors. All of them have their frequency represented as clock multiplier multiplied by some base frequency. Note that the multiplier is locked in the CPU and depends on the specific processor model, while the base frequency should have a pre-determined value set by the specific mainboard. Therefore, overclocking implies either increasing the processor clock multiplier or raising the base frequency. The first approach is somewhat simpler, but requires special processors that allow changing the multiplier (among them are AMD Black Edition or Intel Extreme Edition CPUs). The second approach is more complex, but doesn’t require anything extra from the CPU: its effect depends solely on the mainboard functionality and user’s skills.

The main problem during overclocking by raising the base frequency is the fact that it is tied up not only to the clock frequency of the processor computational cores. It is also used to obtain the values of a number of other parameters: L3 cache frequency, memory bus frequency, the frequency of the bus between the processor and the core logic set, etc. This is where most of the obstacles are: when you increase the base clock and as a result – the processor clock, you should remember that far not all the sub-systems can actually work at proportionally increased speeds. This is where overclocking of AMD six-core Phenom II X6 processors is hardly any different from overclocking of other Socket AM3 dual- and quad-core CPUs. All AMD processors based on 45 nm semiconductor dies have the same exact set of independent frequencies. However, the launch of Phenom II X6 still managed to bring a few changes to the situation familiar to all AMD platform fans. I am talking about the frequency used by AMD Turbo Core technology.

So, there are a total of five frequencies used by platforms on AMD Phenom II X6 processors:

  1. CPU clock frequency. It is usually mentioned among the CPU base specifications. It is the most important system parameter affecting its performance: it indicates the frequency that all processor computational cores usually work at.
  2. CPU frequency in Turbo mode. This is the CPU frequency in all modes with partial load. Namely, Phenom II X6 enables this frequency when three or more cores out of six are idle (this frequency is higher than the nominal).
  3. HyperTransport bus frequency. This bus connects the CPU with the core logic set. For Phenom II X6 processors supporting HyperTransport 3.0 this frequency is set at 2.0 GHz.
  4. Frequency of the North Bridge integrated into the CPU. This is the frequency of the L3 cache integrated into the processor and also the frequency of the memory controller. It is set at 2.0 GHz for all Phenom II X6 processors independent of the CPU model.
  5. Memory frequency. This is the major parameter of the memory sub-system. The memory controller integrated into Phenom II X6 is compatible with DDR2 andDDR3 SDRAM and can clock this memory at 800, 1067, 1333 and 1600 MHz.

Each of these five frequencies is set using a corresponding multiplier and common base clock that is set at 200 MHz for all Socket Am2/AM3 platforms. It can be formally described as follows:

  1. [CPU frequency] = [CPU multiplier] x [Base clock];
  2. [CPU Turbo frequency] = [CPU Turbo multiplier] x [Base clock];
  3. [HT frequency] = [HT multiplier] x [Base clock];
  4. [NB frequency] = [NB multiplier] x [Base clock];
  5. [Memory frequency] = [Mem multiplier] x [Base clock].

All multipliers mentioned above are completely independent and can be changed in the mainboards BIOS Setup. The only limitation to keep in mind when you change the frequencies of different system units, is that the HyperTransport frequency should never be higher than the frequency of the North Bridge integrated into the processor.

The base clock generator frequency that is marked as [Base clock] above is set at 200 MHz in the nominal mode. [CPU multiplier] and [CPU Turbo multiplier] are determined by the nominal frequency of the specific processor model, but can be changed in Black Edition processors. [HT multiplier] and [NB multiplier] are set at 10x by default, but the manufacturer allows lowering them. As for the coefficient used for the memory frequency, its supported range is big enough to ensure processor compatibility with different memory types with up to 1600 MHz frequency when the base clock is at its nominal setting.

For example, here are the numbers obtained for the Phenom II X6 1055T processor working with DDR3-1333 SDRAM:

  1. [CPU frequency]: 2800 MHz = 14.0 x 200 MHz;
  2. [CPU Turbo frequency]: 3300 MHz = 16.5 x 200 MHz;
  3. [HT frequency]: 2000 MHz = 10 x 200 MHz;
  4. [NB frequency]: 2000 MHz = 10 x 200 MHz;
  5. [Memory frequency]: 1333 MHz = 6.67 x 200 MHz.

You can find options for changing all of the above mentioned parameters in the BIOS of contemporary mainboards.

For easier perception some manufacturers display the resulting frequencies instead of the multipliers, but that doesn’t change the essence. Also, they may be using different names for the base clock, such as CU Bus Frequency, like you have just seen on the previous screenshot, HT Reference clock or even CPU Frequency.

It is, however, quite easy to overclock Black Edition processors: you just need to increase the multiplier and you will get higher clock speed right away. The only problem is that Black Edition processors are usually top of the line and most expensive products. For example, if we take six-core CPUs there is only one 300-dollar Phenom II X6 1090T Black Edition CPU. More affordable models do not support this simple overclocking technique. Therefore, Phenom II X6 1055T, for instance, can only be overclocked by raising the clock generator frequency above the nominal 200 MHz. thanks to the fact that the clock generator is actually located on the mainboard and not inside the CPU, the change in its frequency cannot be detected and blocked.

However, the increase in clock generator frequency results not only in the increase in the main CPU clock speed, but also produces higher HyperTransport and memory bus frequencies and affects L3 cache frequency. And these factors could eventually limit your overclocking success. However, luckily, these issues can be easily eliminated by lowering the corresponding multipliers in the mainboard BIOS.

Moreover, you can also increase the voltage of those sub-systems, which frequency potential you wish to increase by overclocking. Although these measures will not only produce higher frequencies, but also higher heat dissipation and power consumption, they become an important part of your overclocking success provided you ensure proper cooling of the system components involved. There are three voltages in Phenom II X6 based platforms that may affect overclocking results:

  1. Processor core voltage. It is the voltage of the CPU cores. For Phenom II X6 processor family is is usually set no higher than 1.4 V. It is considered safe and effective to increase this voltage setting to 1.45-1.5 V when only air-cooling is in place.
  2. Voltage of the North Bridge built into the processor. Alight increase in this voltage above the nominal 1.15 V may help during L3 cache and memory controller overclocking.
  3. Memory voltage. This parameter has an indirect influence on the processor overclocking success. It allows overclocking DDR3 memory.

You can find the options for changing these voltages in the BIOS of contemporary mainboards.

Also, when we talk about voltages, we should keep in mind that processors can adjust their voltages automatically when Turbo Core technology kicks in. For example, processor Vcore rises by additional 0.15 V in turbo mode. That is why this technology can do more harm than good during overclocking.

Everything we have just said makes the general rules of Phenom II X6 overclocking quite obvious at this point. The increase in the base clock frequency plays the primary part in this process. The resulting processor frequency depends linearly on the base clock via a multiplier determined by the model of your processor. However, you have to make sure that the frequency of the North Bridge built into the processor and the frequency of the HyperTransport bus don’t exceed 2.0 GHz that is why you have to lower corresponding multipliers accordingly. The same is true for the DDR3 memory frequency: the actual resulting memory clock shouldn’t exceed what the modules are physically capable of, so you may have to lower the corresponding multiplier as well.

If you would like to additionally improve your overclocking success, you may also raise the CPU Vcore, the voltage on the integrated North Bridge and memory voltage. But in this case you have to pay due attention to heat dissipation and use an efficient cooler. Moreover, you can also benefit from enabling CPU Load-Line Calibration function in the mainboard BIOS. It prevents the processor voltage from dropping when its current goes up.

However, as for Turbo Core technology, I would recommend disabling it. While it makes sense in nominal mode to enable this Turbo technology as the CPU is not working at the top of its abilities, in overclocked more it is useless. You will have to limit maximum processor frequency, since the multiplier used in Turbo-mode is already increased. And it means that the processor clock frequency will be lowered in non-Turbo states when the CPU is not fully utilized. Moreover, if you have already increased processor Vcore manually, then further automatic increase in processor core voltage that accompanies the enabling of Turbo Mode may lower the life span and reliability of your processor.

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