Phenom II X2 550 BE

[Jose]

There were some Phenom2 X3's that could be unlocked to 4 cores and were stable. This only worked with some motherboards and didn't always work, some couldn't even boot, others couldn't be overclocked much, yet others could be overclocked much!
This was a few months ago, when I got a X3 don't know how things are now. Sadly mine is not able to even boot but I find the X3 more than enough for everything. I don't do 3D design/games but that would depend more on the gfx card.
The DD3 memory at 1600Mhz gives a nice boost in performance and the Phenom2's cache seems to have solved the problems that plagued the Phenom1.

[Jose]

@koshman
"@ Jose: try updating your BIOS. A lot of the cheaper 770/785G mobos had problems when ACC was enabled even when the chip itself was not faulty (4th core only disabled) - they usually wouldn't even POST with the original BIOS when ACC was enabled. I've heard lots of reports where a newer BIOS revision solved this problem."

Tried everything already, thanks for the suggestions. I have an AsRock M3A790GXH which has the 790GX chipset. Got it by luck on eBay for 50€ around 6 months ago almost as an accident! It's normally listed as a board which can unlock the 4th core and has the right southbridge to do it.
AsRock has now new top of the range AM3 board so I guess they'll now stop adding "features" to the previous models...

José