The new Intel Xeon Westmere processors that make their Apple debut with the new Mac Pro offer up to six cores per processor. And for $5000, you can outfit a Mac Pro with two six-core processors, for a total of 12 processing cores. That system ships with a 1TB 7200-rpm hard drive, 6GB of RAM and an ATI Radeon HD 5770 graphics card with 1GB of video memory.

The new Westmere processors support Intel’s Hyper Threading technology that can offer twice as many virtual cores (24 in this case) to applications that can make use of them. The processors also use TurboBoost technology to power down those extra cores when idle to provide more power to the one or two cores that a typical application might actually use.

2.66GHz Xeon Westmere 12-core Mac Pro Speedmark scores

If 24 virtual cores seems like a lot, you’re not alone. In our old Speedmark 6 benchmark test suite, we used CineBench R10, which had a hard time using all of those cores; the software crashed when attempting to run the multiple CPU test. Fortunately, CineBench R15 was introduced a few months ago and it supports 24 (and more) processor cores. The updated CineBench test is included in our brand spanking new Speedmark 6.5 test suite, which we used to measure this system’s performance against other Macs.

If the $5000 price didn’t give it away, our tests of the 12-core Mac Pro show that this Mac Pro is not meant for the average consumer. With iMacs and lower-priced Mac Pros outperforming the 12-core model at many everyday tasks, it was only in the handful of high-end, specialized software tests that the 12-core Mac Pro shined. Results from HandBrake, CineBench CPU, and MathematicaMark (all using the available 24 virtual processing cores), were the fastest we’ve seen. The 12-core Mac Pro’s Speedmark 6.5 score was 21 percent faster than the 8-core 2.4GHz Xeon Mac Pro ( ), with a 52 percent higher MathematicaMark score, 36 percent faster CineBench R15 CPU score, and 19 percent faster HandBrake result. The new 12-core Mac Pro was 26 percent faster overall than the new low-end Mac Pro ( ), a quad-core system running at 2.8GHz.

As shown in our "Fastest Macs money can buy" report, the 12-core Mac Pro was not the overall speed king in our tests. It was outperformed by a $3699 built-to-order (BTO) Mac Pro with a 3.33GHz 6-core Xeon Westmere processor, which was faster in 10 of our 17 tests, and matched the 12-core Mac Pro’s scores in two other tests. Testing the 12-core Mac Pro with 12GB of RAM (six 2GB DIMMs provided by Crucial) showed very little improvement over the 12-core Mac Pro with 6GB of RAM—just one Speedmark point.

The 12-core Mac Pro was 34 percent faster, overall, than the 2009 8-core 2.26GHz Xeon Nehalem Mac Pro, and 42 percent faster than the 2009 quad-core 2.66GHz Xeon Nehalem Mac Pro.

Compared to the high-end standard configuration 27-inch iMac with a 2.8GHz Core i5 quad-core processor ( ), the 12-core Mac Pro was 33 percent faster overall. Looking at some BTO options on the iMac, however, the iMac fares better and costs considerably less. A 2.93GHz Core i7 quad-core iMac costs less than half as much as the 12-core Mac Pro, which was just 17 percent faster overall—almost all of the performance benefit of the 12-core Mac Pro was in our multi-processor savvy application tasks. The 12-core Mac Pro was 37 percent faster in our HandBrake test, 73 percent faster in our CineBench CPU test, for example.

You can see all of the individual test results that make up our Speedmark 6.5 test suite.

Macworld’s buying advice

The 12-core Mac Pro is certainly not for everyone. It is expensive and unimpressive when performing everyday computing tasks. However, for anyone who makes a living working on high-end applications that can use and abuse the 24 virtual cores, the amount of time saved on processor-intensive tasks results in the 12-core Mac Pro being a bargain.

[James Galbraith is Macworld’s lab director.]