Athon Thunderbird vs Athlon

I think you are referring to the older Slot-A Athlons versus the newer verion of socketed Athlon called the Thunderbird. The difference between the two is the L2 cache being 256k on die and running at full processor speed with the T-bird. The older slot-A Athlon had 512k off die cache running at some fraction of the core processor speed, depending on speed of the processor. Overall, the T-bird is faster because the L2 cache runs faster.

Scout