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Overclocking and Core Unlocking

We know the overclocking potential of modern Phenom II processors well enough. Using air coolers, they can be clocked at frequencies up to 4 GHz. The new models can hardly change this much, but we can expect a certain increase in maximum frequency due to tech process improvements. So, we checked out the overclockability of each of the three new CPUs we had in our hands.

First we took up our Phenom II X6 1075T. This is an ordinary member of the six-core family and does not have an unlocked multiplier. Therefore, it can only be overclocked by increasing the base clock rate above 200 MHz.

We eventually made it stable at the expected frequency of 4.0 GHz. The base clock rate was set at 268 MHz and the CPU voltage was increased to 1.525 volts. As the screenshot shows, the overclocked CPU had a normal temperature: occasionally higher than 70°C according to the under-socket sensor during our stability check. It must be noted that we did not reduce the frequency multiplier of the CPU-integrated North Bridge, so the frequency of the memory controller and L3 cache grew up proportionally to the CPU frequency from the default 2.0 GHz to 2.68 GHz. Thus, the new Phenom II X6 1075T is no different from other six-core AMD processors in terms of overclocking potential.

Next we tried our Phenom II X4 970. It belongs to the Black Edition series and can be overclocked by changing its frequency multiplier.

Our Phenom II X4 970 was stable at clock rates up to 4.0 GHz (with air cooling). Thus, this new quad-core processor from the Phenom II series has the same overclocking potential as the rest of Deneb-core CPUs we have tested so far. The CPU-integrated North Bridge could be overclocked up to 2.6 GHz. To make the CPU stable we increased its voltage to 1.525 volts and the North Bridge voltage to 1.25 volts. When passing our stability tests, the CPU was as hot as 65°C according to the internal sensor which reported far more credible numbers than the under-socket one.

So, if off-the-shelf Phenom II X4 970s overclock better than the test sample, as AMD has promised to us, we can expect them to become highly valuable for Socket AM3 overclockers. This needs checking out in practice, of course.

Our third processor, the inexpensive Phenom II X2 560, is Black Edition, too. Besides that, it resembles the Phenom II X4 970 being based on the same Deneb die (with two cores turned off). That’s why our Phenom II X2 560 shows similar overclocking potential to its quad-core cousin.

However, we made our Phenom II X2 560 stable at 4.0 GHz using a lower voltage (1.5 volts). The CPU-integrated North Bridge worked at 2.6 GHz at a voltage of 1.225 volts. Interestingly, although we used almost the same voltages and frequencies as with the six-core and quad-core CPUs, the dual-core CPU had a much lower temperature.

However, it is not with sheer overclockability that the Phenom II X2 560 can excite an enthusiast. The more thrilling thing is that this dual-core CPU incorporates two disabled cores which you can try to turn back on. This is quite easy to do on most mainboards if the Deneb die this CPU is based on has no defects in the disabled cores: nearly every mainboard maker has implemented such a technology. By simply choosing an appropriate BIOS option or setting an onboard jumper, you can turn your Phenom II X2 560 into a quad-core Phenom II X4. This is not 100% guaranteed, but the mature 45nm tech process makes it far more probable. Our test sample transformed into a quad-core CPU without a single problem. Moreover, we overclocked it then to 3.9 GHz.

By the way, if your Phenom II X2 560 doesn’t work in quad-core mode for some reason, you can try to enable only one of the two disabled cores as modern mainboards offer this opportunity, too. So, a $100 Phenom II X2 560 can make a very valuable purchase because, with some luck, you can not only overclock by 20% but also double the number of its execution cores!

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