Unlocking fourth core on Athlon II X3 revision C3 CPUs

First triple-core Athlon IIs were rebranded Phenom II X4 Deneb processors with L3 cache and one core disabled. Computer enthusiasts quickly learned that the cache and/or the core could be re-enabled by setting "Advanced Clock Calibration" feature in BIOS to "auto". Once Athlon II X3 line of processors switched to native Rana core, which was nothing less than Athlon II quad-core "Propus" core with one core disabled, the same trick could be used to unlock the disabled fourth core. Sadly, there was no integrated L3 cache in this core, so it was not possible to unlock one. With introduction of newer C3 revision of the core, we wanted to check whether the old ACC trick would still work. As we already posted before, we acquired triple-core Athlon II processors with newer core revision, and we tried to unlock the 4th core on all of them. We were able to successfully unlock two out of three processors, which, in our opinion, is pretty good result. Unlocked CPUs passed all tests. Unlocked Athlon II X3 435 was reported by BIOS as "AMD Phenom(tm) II X4 B35 Processor", and unlocked 440 model is reported as "AMD Phenom(tm) II X4 B40 Processor". It's not clear why BIOS identifies the processors as "Phenom II", when, as screenshots show, they don't have L3 cache. We couldn't unlock the 4th core on the third processor, Athlon II X3 405e. After enabling ACC feature in BIOS, the system refused to post.

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How to Unlock

2011-01-19 16:27:51
Posted by: George Px

Get a motherboard that has the BIOS feature to unlock the 4th core, and set the calibration to overclock the CPU to AUTO. ASRock and ASUS motherboards for the AM3 form factor in the $50 to $60 range are usually good bets for this unlocking.

How to

2010-11-03 11:44:08
Posted by: Adrian

How do I unlock?

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