AMD Phenom II X2 555 Black Edition no broken cores

Uh, no. That's why it's sold as a dual core, because they either need to meet demand for that particular chip, OR because they are defective. NEVER buy a chip thinking that you will be guaranteed to unlock it.

Yup. Any X2/X3 is not guaranteed to have stable cores. That's why when you purchase your chip, don't base your purchase on an X2/X3 solely on the idea that you WILL be able to unlock it successfully to try and get a quad-core at a reduced price. The chances are you'll be disappointed.

If you want an AMD X4, get the 955. If you want a really fast AMD X2 with the chance to make it an X4, get the 555.

The only reason Phenom X3/Phenom II X2+X3/ Athlon II X3 processors were released was so AMD could sell processors that had a defective core and still make money on it rather than throwing it away. Because these parts proved popular, they've had to disable cores on perfectly working quad core processors to meet sales demand. When you buy one of these, it may really have defective cores, or it may have working cores disabled to meet demand.

I have one and it has 3 working cores and 1 defective one.

Mactronix  

Purchased a 555BE on saturday and unlocked both locked cores with zero headache and a minor increase in voltage to remain stable.

Aint it great?
My 555 broke 4.0 ghz stable with no voltage increase. 3.8 as a quad.
I like my 550 but I love my 555!

Check that. After more fiddling I found that Core 2 was making popping and snapping sounds in games. I have disabled Core 2 and games run fine. Prime95 and 3DMark06 run fine just games produce the popping and snapping out the speakers.

I'm not too terribly upset becuase I'm still going to push the OC with three cores. Funny thing is in CPUZ it lists my CPU as an Athlon II X3 455 but its specification is Phenom II X4 B55