For example, in preliminary testing I used an HP ProLiant DL580 with four quad-core Intel Xeon X7350 CPUs running at 2.93GHz per core as a baseline. The Nehalem system was running two quad-core Intel Xeon W5580 CPUs at 3.2GHz per core with HyperThreading enabled.
Averaged across all tests, the Nehalem system was roughly 60 percent faster than the X7350-based server. For instance, the time required for the X7350 system to encode 16 identical 200MB WAV files to MP3 at 224Kbps was 77 seconds. The Nehalem system completed the task in 40 seconds. The gzip tests showed the X7350 compressing the 16 resulting MP3 files in 6 seconds, while the Nehalem system completed the task in 2 seconds. For a single-thread test, I converted a 27MB MPEG-4 file to FLV (Flash Video) with MEncoder. The X7350 took 43 seconds at roughly 100 frames per second; the Nehalem took 27 seconds at roughly 163 frames per second.
Without a doubt, these numbers are hugely impressive, even if they are measured against a Tigertown-era chip. A dual-socket Nehalem system handily beats a four-socket X7350 system across the board. And the tests were run with 16 concurrent single-threaded processes, so while the X7350 used one physical core per process, the Nehalem, using HyperThreading, ran two processes per physical core.
As far as power consumption goes, 2cpu.com's Micah Schmidt put it this way: "In identically configured Supermicro workstations, the Nehalem-based Xeon W5580 system draws an average of 70 watts less than the Harpertown-based Xeon X5492 system at idle. Coupled with the additional performance of the new processors, the performance-per-watt difference is huge."
Finally, a V-8 platform that's worth the money. Half the cores at half the power in a 55xx Xeon is twice as fast as twice as many cores in older chips. That's Moore's law back on track.