Lostcircuits published a really interesting article about AMD´s Phenom processors. Really worth a read - AMD’s Phenom Processor - Beyond Erratum 298. It explains the Erratum 298 (the TLB bug) and makes some interesting statements about the performance:
Arguably, there is that thing called legacy support and legacy applications are still prevailing in today’s computing environment. On the other hand, there are truly multithreaded applications and as it turned out, the more thread level parallelism is used in any application, the better fared the Phenom processor. There is a bit more to this. Multicore processing is fine and dandy as long as the access to the data is warranted. Otherwise, there is starvation of the cores.
With a highly threaded application, the Pheonom can compete with a higher clocked Core2-based processor. On single thread load, the Phenom has problems to be as performant as the Intel products. This situation sounds familiar to me …