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Overclocking

Socket AM3+ platform and FX-series processors are positioned as overclocking-friendly right from the start. This follows not only from the fact that all FX processors have unlocked multipliers, but also from a number of extreme overclocking experiments supported by AMD, in one of which they set an overclocking world record using a new FX-8150 processor. The company’s statement about the new microarchitecture being well-optimized for work at high frequencies also seems very promising. Could it be a new overclocking wonder? Let’s find out.

It is extremely easy to overclock any FX processors: their logo states “Unlocked” for a reason. You can change the processor clock frequency by changing its multiplier right in the mainboard BIOS Setup, or via special utilities from AMD (Overdrive Utility) as well as from mainboard vendors. You can also overclock the integrated North Bridge and system memory in Socket Am3+ system the same way.

During our tests we managed to get our FX-8150 to work stably at 4.6 GHz. For increased stability we raised the processor core voltage to 1.475 V and enabled Load-Line Calibration option. During our stability tests the CPU temperature at this frequency didn’t exceed 85°C, according to the under-the-socket diode and 75°C, according to the integrated thermal diode in the CPU itself. As we have already said, we used a very efficient air-cooler – NZXT Havik 140.

Note that we also tried to simultaneously overclock the North Bridge integrated into the processor, because increasing its frequency will have a positive effect on the L3 cache memory and memory controller performance. However, unfortunately, we couldn’t get past 2.4 GHz frequency even though we tried to raise its voltage as well.

In any case, the result of our FX-8150 overclocking experiment – 4.6 GHz frequency – is a definite success, especially since AMD Phenom II processors rarely overclocked beyond 4.0 GHz with air-cooling. In other words, Bulldozer microarchitecture really managed to push the frequency maximums somewhat further away.

However, we should actually compare the results of our FX processors overclocking with those of Intel Core i5 and Core i7 processors for LGA1155 systems. And these guys overclock just as good. For example, Core i5-2500K will typically overclock to 4.7 GHz under an air-cooler and with the Vcore increased by 0.15 V. and in this comparison, FX-8150 doesn’t look so victorious anymore.

Our impression from Zambezi overclocking will be spoilt even more if we compare the performance of the overclocked FX-8150 and Core i5-2500K (the increase compared with the nominal mode is given in brackets):

Overall, overclocking doesn’t really change the situation. However, in those applications where FX-8150 was faster in nominal mode, the gap is no longer that dramatic. And in those tests where Core i5-2500 was ahead, it managed to strengthen its positions even more. In fact, it is not surprising at all: the clock frequency of our FX-8150 processor increased by 28% during overclocking, while the frequency of Core i5-2500K got 42% higher. Moreover, as we can tell from the way the frequency grew during overclocking, Intel Sandy Bridge microarchitecture is more sensitive to frequency increase. In other words, even if we take into account overclocking, the new Bulldozer processors don’t look superior to Intel’s ones, even though they overclock pretty well.

 
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