Although the idea of a processor with 3 cores sounds strange to many, AMD has managed to make a reasonable success with the Phenom X3 and Phenom X3 II. In both cases, the version with 3 colors are nothing more than quad-core processors with defects in manufacturing, where the core is disabled in damaged plant, resulting in a processor perfectly functional, but with only 3 active cores, the AMD can sell for a lower price.

The secret they do not count is that many of the series X3 processors are actually quad-core processors perfectly functional, they have simply turned off one of the colors to meet the demand of the market. After all, the rate of defects in processors ranging from an unpredictable way, but the demand for each mode remain more or less stable month to month.

In most cases, the deactivation of the nuclei of the cache, or any other internal component that the manufacturer disable resolve to differentiate the model consists of only one variable in the microcode of the processor, which causes it to ignore the component and if behave as desired.

In case of Phenom II, however, a bug in the firmware (or maybe an accidental breach by AMD) provides that the fourth nucleus is enabled via software, from commands sent by the motherboard. The "hack" works on many boards that use the chip as SB750 south bridge, and can be enabled through the "Advanced Clock Calibration" in the Setup. Just leave it with the "Auto":

This is an option originally designed to increase the tolerance of the processor to errors, so that old models of Phenom overclocks reach a little higher, but in the case of the Phenom X3 II she won an unexpected survival.

If your motherboard is compatible, just turn it so that the system will use the fourth core (just check if there is a quarter meter in Windows Task Manager, or the output of command "cat / proc / cpuinfo" on Linux), essentially turning your 7xx Phenom X3 Phenom X4 on a 9xx.

The possibility of an extra free performance eventually attract a lot of attention, causing many people buy an X3 in the hope of "winning" a free X4. The subject has such repercussions within technical circles that many have raised the possibility that this would be a deliberate breach of AMD to gain some additional sales in a difficult season.

Indeed, despite the hype, the success rate is relatively low. First, a relatively small number of cards are capable of releasing the fourth nucleus and other you need to use a specific version of the BIOS to succeed.

Moreover, even where the fourth core is activated, it will only work on a stable if you give the chance to take in hand one "good" processor, where the fourth core is not a defect and was only for disabled complete the number of units required. If the fourth nucleus is really bad, turn it will not do any good, since that will only display errors or the system hangs when it is used.In other cases, the fourth core can operate without errors, but only to the default frequency (eliminating the possibility to overclock) or only work at frequencies lower.

In practice, the possibility of success is small and the difference in performance between three and four cores is not very large to initiate a conversation. Taking all this into account, it makes little sense to waste time hunting processors or boards in which the hack works. At the end of history, who left the AMD has been winning, you just selling more processors for the most curious of duty. :)