I guess this has been discussed already, but what do you make of the guy's analysis:

AMD's official Barcelona show:
http://www.youtube.com/watch?v=VGiv9Dtrc5Q

In POV-Ray, 4 Barcelona (16cores total) got about 4000 pixs /sec.
while the 4 Opteron DC(8 cores total) in the same frequency got about
2200 pixs /sec.

Compare with the test provided by xbitlabs:
http://www.xbitlabs.com/images/cpu/intel-v8/povray.png
http://www.xbitlabs.com/articles/cpu..._11.html#sect0

Two X6365(Quad Core Xeon @3.0GHz), 8 cores total can do 4677 pix/sec.
And two FX74 (Dual core K8 @ 3G, 4Cores total) can do 2020.

combine all the facts above together, we can find out that the test
systems in AMD's show are running at about 2GHz. At these frequency,
the 16 cores Barcelona system even can't beat current 8core Xeon
system.

Remember the Quad core Barcelona will top at 2.5GHz! And Intel's
Harpertown in on the way.
....