IIRC, that's maybe a 16x improvement (32x if you count 32->64 bit). Which accounts for less than half of the (orders of magnitude of) improvement we should have got from Moore's law.

(More cores aren't a performance improvement; if you were willing to deal with non-serial execution, you could have just bought 32 Pentium Fours; putting them all on the same chip is convenient (and cheap), but as a price/performance improvement, it's all price, no performance.)