Letters and numbers on processors... what do they stand for?

[GPT]

Phw, I hope no one saw that, mo-o-O-O-HA-HA-HA

Thanks to the "edit" button I now may  rest in peace
 knowing the fack that I used it :-D ;-)

Happy X-MAS (did I spell that right it's looks "wrong")

[GPT]

I was total wrong XC stands for "partial quality" MC is for full quality.

The four quality grade:

MC   = Full quality
XC   = Partial quality
PC   = Product engineering
SPAK = Sample pack

And I think that RC "points to the processor speed" next to the Letters.