I would kill for an AMD manual that could actually make sense of this coding. This code doesn’t change, it morphs.:)
This is not about the codes that AMD explains in its tech documents, this is about the codes that they don’t explain.
That being said, there seems to be some sort of progression indicated by the coding. We do know AMD revises a lot; the CPUID of 642 covers at least seven minor revisions. We also know they put out CPUs with different codes in the same week.
Over time, the second and third letters in the first block of four letters have crawled up the alphabet. The initial Dresden chips, for instance, started with ADEA and AEEA. Later, we saw AJEA.
Now we are seeing Dresden letterings like AVFA, BVFA, AXHA, BXHA, and, the latest I’ve seen, AXIA. All these, BTW, were being made in the third week of 2001.
Note that the fourth letter remains the same. Until a couple weeks ago, neither did the first, that was always “A” too. We’re now seeing “B”s. Clearly that signifies something, but what?
I can come up with a couple plausible explanations, but then I can come up with just as good arguments as to why I’m wrong. 🙂
The only thing I think we can rely on is that the later in the alphabet the second or third letters are, the later the process. And of course, they’re running out of letters in the alphabet. 🙂