With one of the best overclocking tricks since the one with the pencil, many unassuming Athlon II X3's hide an unused but perfectly functional 4th core under that shiny heatspreader.  The flick of a BIOS setting will tell you if you can try to pull this trick off, though stability testing is very important as some of the cores on these CPUs are disabled for a good reason.  Legit Reviews did exactly that with an AMD Athlon II X3 445 and it turned out that they were unlucky enough to receive one with a faulty fourth core.  They did get plenty of benchmarks from the three cores that worked though.

"The AMD Athlon II X3 445 was a processor I was looking forward to working with when the

opportunity had presented itself. Not necessarily because it is going to be the fastest

processor out there, but it only has three active cores. Whats that mean? Well, that most likely

there is a fourth core under the heat spreader. With any luck I would be able to unlock the

fourth core, and be able to test the AMD Athlon II X3 445 as a Quad Core as well. Fortunately

there was a fourth core on the AMD Athlon II X3 445..."

Here are some more Processor articles from around the web:

  Processors

• AMD Athlon-II X4-640 Processor @ Benchmark Reviews
• Athlon II X4 640 vs. Core i3 530 CPU Review @ Hardware Secrets
• Intel i5 655k @

  Overclockers.com

• Intel Xeon 5680 Chips Served on EVGA SR2 @ KitGuru
• Intel

  Core i7 875K @ Hardwareoverclock