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AMD Phenom II X4 940 Black Edition

Overclocking revisited.

August 31, 2009

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Overclocking, Zalman CNPS9700 NT

This model of an air cooler is not the best there is, but its high efficiency has been proved many times in practice. It's not difficult to find such coolers in stores, they are easy to install, no extra efforts involved.

None of the processors cores operating at 3600 MHz grew above 60°C during the stability test -- that is better than the boxed cooler by 10°C.

However. further frequency growth faced unsurmountable problems. The processor successfully loaded the operating system at 3800 MHz, however it failed the stability test after several minutes already. Increased voltage did not change the situation -- the processor remained unstable even at 1.60 V.

Having set the multiplier to 18.5 (3700 MHz), our Phenom got back to the stable track and added only 1°C under peak load. Further growth of the clock rate reveals the maximum stable CPU frequency of 3775 MHz (204x18.5). We are a little disappointed with our sample with its low overclocking potential. But that's overclocking to you, no one can predict how much you will gain.

  AMD Phenom II X4 940 Black Edition 3775 MHz
WinRAR 3.71, s 52
7-Zip 4.57, s 137
x264 v0.59.819M, fps (1pass/2pass) 78.17 / 21.38
3DMark Vantage, 3DMark Score (CPU Score) P10378 (12448)
PCMark Vantage, PCMarks 5641

There are no mistakes in the table -- result of this processor in PCMark Vantage is indeed lower than it demonstrated at 3600 MHz. This behavior indicates inadequate software (quite possible) or incorrect operation of the processor at this frequency. However, the other tests show apparent performance gains, and the stability test has never crashed.

Overclocking CPU NB

As you may know, memory controller in AMD processors has been integrated into the processor core for a long time already, so a processor does most work of the Northbridge on a motherboard. To make a CPU work faster with memory and L3 Cache, we should accelerate CPU NB.

It can be done by raising the multiplier as well as by increasing the clock frequency. By default, CPU NB operates at 1800 MHz (200x9). In practice, maximum stable frequency of CPU NB does not decrease as processor cores are overclocked.

For example, when the CPU multiplier is set to х15, the master clock frequency is raised to 204 MHz, and the memory multiplier is reduced, CPU NB may work well at 2448 MHz (204x12) without raising the voltage. Overclocked to maximum, this unit still worked well at 2448 MHz, although we had to increase the voltage by 0.05 V to pass the LinPack test.

  AMD Phenom II X4 940 Black Edition 3775 MHz, CPU NB 2448 MHz
WinRAR 3.71, s 49
7-Zip 4.57, s 126
x264 v0.59.819M, fps (1pass/2pass) 80.87 / 21.84
3DMark Vantage, 3DMark Score (CPU Score) P10431 (12573)
PCMark Vantage, PCMarks 5641

As you can see in the table, CPU NB acceleration has a positive effect on the overall performance level. In this connection we shouldn't forget about this component, when you overclock your processor with the multiplier alone.

AMD Overdrive 3.0.2

This program allows to control practically all important options to overclock a CPU, a chipset, and memory directly from Windows, which theoretically makes overclocking easier, more convenient, and allows to find optimal parameters much faster.

This program is absolutely free, you can download the latest version from the AMD website. It works in two modes -- simple and advanced. Along with overclocking options, it shows system information (table, full list, or diagram), includes a benchmark and a stability test. Overdrive also allows to control fans, but this feature works only if Smart Fan is enabled in BIOS, so that you can slow the fan down to 25% of the nominal speed.

Overclocking in the simple mode is limited to a single slider, its minimum corresponds to the default settings, and its maximum raised the CPU multiplier from 15 to 16 in our case, which overclocked the system by 6.7%. Not much, but safe and easy even for the youngest gamer. An alternative to the slider is automatic detection of the maximum frequency. When activated, AMD Overdrive will start to slowly accelerate the clock generator and check its stability. The current version of the program does not reduce the memory multiplier during the tests. As a result, the program quickly reports about the maximum frequency reached, having no idea that it's also possible to raise the CPU multiplier by at least 0.5. Well, that's the automatic mode, you cannot expect miracles from it.

The advanced mode is a little more interesting, which offers a huge number of manual settings, including a full set of memory timings. All would be good, but for one but -- for some unknown reason, the program would set the wrong frequency for PCI Express, raising it to 142 MHz (while the standard is 100 MHz). Manual control reduction would not help. The frequency would still jump up to that value. As a result, our tests ended up with a blue screen of death and removal of the program in the safe mode. Let's hope that it's atypical behavior, and this utility works better in most cases.

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Page 1: Introduction, CPU: boxed cooler

Page 2: CPU: Zalman CNPS9700NT, NB, Overdrive

Page 3: RADEON 4890, AMD Fusion For Gaming 1.0

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