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Unlocking Blocked Cores

I don’t think I need to remind you about the most important news of the triple-core Phenom II X3 launch back in the days. Since these processors were based on the same quad-core semiconductor dies as the Phenom II X4 solutions, it turned out possible to unlock the deactivated core and turn this processor into a quad-core one. And the greatest thing about it was no need for any hardware modifications: all you had to do was to check the corresponding BIOS option responsible for Advanced Clock Calibration (ACC) function. Of course, you may not be able to enable the fourth core on some processors, only on those using a fully-functional semiconductor die without any defects. Luckily, the probability of getting a “good” CPU sample was pretty high for the first batches of Phenom II X3 processors and the trick with unlocking the fourth core helped increase the popularity of this AMD solution.

Many enthusiasts are anxious to learn if the same can be done for the new dual-core AMD processors. Let’s find out.

First we would like to remind you that the idea of unlocking blocked cores is only valid for Phenom II X2 CPUs. Its younger brother, Athlon II X2, is based on a dual-core die right from the start and there is nothing to unlock there.

Secondly, the implementation of Advanced Clock Calibration technology in the BIOS of many mainboards has changed, since the launch of Phenom II X3 processors. AMD wasn’t going to watch the enthusiasts raving about their success in unlocking additional cores and tried to force mainboard makers to update their BIOS code with the new versions offering no options for core unblocking. But luckily, not all mainboard makers complied with AMD’s wishes. For example, new BIOS updates for the Gigabyte MA790FXT-UD5P mainboard that we use in our testbed even got an additional option that offers you to choose between two BIOS versions: new one without the option for unlocking blocked processor cores and old one with this option.

This option is called EC Firmware for Advanced Clock Calibration. You have to set it “Hybrid” and then enable Advanced Clock Calibration in order to be able to activate the processor cores, like you did before. And to our great joy we can assure you that it works not only for Phenom II X3, but also for the new Phenom II X2 processors.

We managed to activate both blocked cores on our Phenom II X2 550 sample and turn it into a fully-functional quad-core CPU without any effort. By the way, it immediately overclocked to 3.8GHz.

In other words, dual-core Phenom II X2 550 could, in fact, be a high-performance quad-core processor. But it also could not be one, because everything here depends on the semiconductor die used: if it is a fully-functional die with two blocked cores or a die with two defective ones that have been blocked. And considering the fact that AMD is going to price their dual-core processors very democratically, there is really little chance of unlocking the blocked cores successfully. We believe you have more chances of coming across fully-functional Phenom II X2 processor samples only in the first CPU batches. So, if we are seriously hoping to get a “lucky” dual-core, then we would strongly recommend that you do not to put it off for long.

Besides, do not forget that it is not enough to have a “lucky” Phenom II X2 processor. You also need an appropriate mainboard that should be able to enable ACC “the old-fashioned way”. AMD is currently working very hard to ensure that these boards become as few as possible.

By the way, we have to point out that Phenom II X2 with unlocked cores does in fact differ from the real Phenom II X4. Firstly, the mainboard recognizes it as some mysterious Phenom II X4 B50 CPU. And secondly, unlocking blocked cores sets processor thermal diodes out of service, just like in case with unlocking the third core in triple-core processors.

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