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Overclocking AMD Athlon 64 and Sempron Socket 754 and 939

AMD Athlon and Sempron processors which are burned at 0.09 microns leave a lot of room for overclocking. The heat dissipated from these processors is quite low which increases the chances of elevating increments in frequency without overheating the system. Before starting this process one must install CPUZ, Motherboard Monitor, OCCT and Super Pi for testing out the entire system while overclocking. For both AMD Athlon and Sempron one must know about the operating frequency and the corresponding formula HTT frequency. The HTT frequency should be implemented stepwise and while constantly monitoring the vital stats for the computer.


The generations of CPU burned at 0.09 microns (commonly known as Venice core for Athlon or for Sempron to) give some room for overclocking.

The heat loss of this generation of CPU is low, allowing substantial gains in frequency, without significant heating (assuming that you are equipped with a well-ventilated housing and a good cooler).

These developments allow you to mount a low-cost configuration, matching in performance with a much more expensive CPU.

Note that: this practice can lead to serious malfunctions of your system, or irreversibly damage some electronic components.

It is recommended to download and install:
  • CPUZ, in order to monitor changes in the frequency of your system.
  • MotherboardMonitor to monitor the temperature of your system.
  • OCCT and Super Pi to test system stability.


For sockets 754 and 939 or the latest AM2 (+) which manages the DDR2, the approach is largely the same.

The 64-bit AMD processors need particular attention. To achieve a good overclocking, there are three things you should master:
  • The HTT, which represents the operating frequency of the CPU set at 200Mhz by default for these platforms.
  • For socket A, it was called FSB.
  • Multiplied by the coefficient (which is blocked by AMD, except for FX) of CPU, it gives the working frequency of the processor.
  • E.g: For an athlon 64 3000 + running at 1.8 GHz:
  • HTT Frequency = 200 multiplied by the coefficient (9) = 1800Mhz
  • The HT or Hyper Transport bus, not to be confused with the HTT.

It is the main feature of these motherboards; it is a dedicated bus for exchanging information between the chipset and the CPU.
Its frequency is 800MHz for most of Socket 754 and 1000Mhz for socket 939.
Beyond this frequency, we find the HTT (200Mhz) to which a multiplier is applied.
Problem: this bus does not support almost any elevation, but we shall learn more about this later.
  • The memory frequency

By default, it is better to make use of DDR400; in this way it will be synchronous with the HTT.
In all cases, behind the choice of the BIOS frequency, this cache hold a ratio of 1:1 to HTT (for DDR400).

----------------------------------------- --------- -------------------------

That's the basics of AMD platform.

From there we will increase the HTT.

We increase this parameter via the bios to 205, then 210, then 215, and... crash!
This is because the HT bus do not support a significant increase.
Pushing the HTT to 215 implies that the bus has passed to 1075Mhz (Example: the Athlon 64 3000 + socket 939) and behind this is the frequency there's multiplier x5. Most BIOS will not support this frequency.
  • So we will limit the multiplier to 4x (4 x 200 = 800) and never exceed the maximum value of the HT bus(1000 in our example, and do not worry about the possible drawback in performance by lowering it, because it can drop to 600Mhz without experiencing any loss in computing power).

Never increase the HTT too fast, do it gradually, + 5MHz each time, testing out the system every time, and monitoring the temperature.

(215, 220, 225, 230...)
  • At this point the PC is unstable and it is the RAM that is causing the problem.
  • Our CPU is still at 9 x 230 = 2070 Mhz, so a little more than a 3200 +.
  • The HT bus is 4 x 230 = 920, at this level everything is fine.
  • But it is possible to go further, because in reality it is likely that your DDR400 can be pushed to 230, is already showing its limits.
  • The first solution is to make use of quality DDR533 RAM, which will leave a good margin for overclocking.

This solution has the advantage of making the memory sync with the HTT, which helps maintain a high bandwidth, especially on sockets 939 that operate in dual channel mode. This will result in a significant overall performance, but will cost you some bucks,
  • The other solution is to desynchronize the memory.
  • This is the cheapest approach, but a good DDR400 will be required.
  • Setting the memory frequency in the bios to "DDR333 (PC2700), we thus apply a ratio of 9/11 between the frequency of the CPU and the one HTT (DDR333 in our example).

So when we are at 230Mhz for HTT, the memory frequency amounted to 230 x 9/11 = 188Mhz.
  • At 240 HTT, a 196Mhz DDR is perfect.
  • The HT stands at 960, that's good.
  • The CPU is now running at 2160Mhz, which is practically equivalent to a 3500 +!
  • To check, just test your configuration with any benchmark software.


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