Source: http://www.nehalemnews.com/2008/07/benchmarks-bloomfield-and-gainstown-vs.html
Thanks to Hornet331 over on Xtremesystems.org for investing significant effort in compiling some excellent graphs for a number of benchmarks provided by JC and others in the Bloomfield thread giving us these great comparisons... (click to enlarge)
I think Extelleron summarized this best with his comments:
You do realize what you are comparing here?
8 Barcelona cores @ ~2.4GHz vs. 4 Nehalem cores @ 2.93GHz.
8 Barcelona cores @ 2.4GHz under 64-bit (which improves performance by 15-20%) are losing to 4 Nehalem cores @ 2.93GHz under 32-bit.
Granted your numbers are a bit lower than they should be for a Barcelona system. If you read Anandtech's MP Barcelona review, Dual Opteron 8356 (2.3GHz) score 14,487, under 64-bit. Were Nehalem also in a 64-bit environment, that would mean that 4 Nehalem cores @ 2.93GHz would be a good 15% faster than 8 Barcelona cores @ 2.3GHz. Work that out and that means that 4 Nehalem cores are not that far behind clock/clock parity with 8 Barcelona cores.
If you look at the Gainestown DP results, they are just as impressive. With SMT enabled (full 16 threads, for some reason only 8 threads were run), Dual Gainestown @ 2.4GHz will effectively tie Quad AMD Opteron 8356 @ 2.3GHz in! Cineben ch 64-bit.
Now imagine the performance of Quad Beckton (32 cores, 64 threads, 24MB L3/CPU) and you know that AMD is in trouble.
Follow the discussion here (about mid-page).