Benchmarks: the unofficial eight-core Mac Pro
Published: 14 Nov 2006
We might be ahead of Apple's product release cycle, and we've probably violated our Mac Pro's warranty, but we just had to see what the Apple Mac Pro could do when populated with a pair of Intel's brand-new quad-core Xeon 5355 processors.
The quad-core processor era was ushered in with the release of quad-core processors for enthusiasts (the Intel Core 2 Extreme QX6700) and for servers and workstations (the Intel Xeon 5355) -- and Intel was kind enough to supply us with a pair of 2.66GHz Xeon 5355 processors. As the Xeon 5355 is pin-compatible with the Xeon 5160 processors that came installed in our Mac Pro, we proceeded to swap out the two dual-core processors with the new quad-core processors.
Incidentally, we strongly advise you not to try this at home: the Mac Pro case is not designed to allow the end user to perform CPU surgery -- and we've got the cuts and bruises to prove it!
With the pair of Xeon 5355 processors installed, we booted the system back up and were greeted with eight active processing cores in both Mac OS X and Windows XP via the Boot Camp Public Beta. With the transplant successful, it was time to run our benchmarks.
Even though dual-core processors have been around for a while now, you'd still be hard-pressed to find many mainstream applications that can efficiently take advantage of both processing cores at the same time (typically referred to as a multithreaded-application). Double that number to four processing cores, and the list of supported multithreaded applications gets even shorter. Double it again to eight -- you get the idea. Some professional multimedia and scientific applications, however, are designed to take advantage of as many processors as are present -- and performance will scale accordingly, based on the number of processors available.
Both the Cinebench and PyMOL tests use all available processing cores and hit 100-percent total CPU utilisation on every configuration we tested. We saw a 31 percent performance increase on the Mac OS X version of the Cinebench test from the two dual-core chips to the two quad-core chips. Although we doubled the number of cores, we didn't see twice the performance. There are a few reasons for this: the quad-core chips are actually running at a slower speed (2.66GHz) than the dual-core chips (3.0GHz). Also, the extra cores introduce some additional computational overhead to the overall workload. Additionally, our 'octo-core' testbed is our own unsanctioned unit, and therefore isn't benefiting from any of Apple's inside knowledge, such as firmware and driver updates to better optimise the system for the additional cores.
Our multimedia multitasking test performs a QuickTime encode in the foreground while iTunes is simultaneously encoding in the background. On systems with two or fewer cores, this workload typically saturates the total CPU utilisation at 100 percent. With four cores, the system hovered around 40-percent CPU utilisation, but dropped to about 23 percent when using eight cores. Interestingly, the actual performance gain we saw between four and eight cores was less than 10 percent. To truly see a significant benefit from the additional cores while performing multiple tasks, you will have to perform a massively multitasking scenario -- something we unfortunately did not have time do for this article.
Our iTunes and Quake 4 tests are more representative, however, of what you are likely to see with most mainstream applications in a non-multitasking scenario. The results for both of these tests (as well as with other programs, not shown here, such as Photoshop CS2) indicate that what influences the speed of these tasks is primarily CPU clock speed. Four cores running at 3.0GHz consistently outperform eight cores running at 2.66GHz. Note that iTunes is better optimised for the Mac OS, while Quake 4 is better optimised for Windows XP.
It will be interesting to see how long it is before Apple migrates the Mac Pro over to the new quad-core Xeon chip and makes an eight-core system publicly available. But unless you do work normally relegated to high-end workstations, perform massively multitasking workloads, or just want the bragging rights, eight cores is definitely overkill -- at least for now. However, as more applications become available that support multithreading across multiple processing cores, the benefits of quad-core and octo-core systems will be realised.
System configurations
Intel QX6700: 4 cores @ 2.66GHz, Windows XP
Windows XP Professional SP2; 2.66GHz Intel Core 2 Extreme QX6700; 2,048MB DDR2 SDRAM 800MHz; 256MB ATI Radeon X1900; 74GB Western Digital 10,000rpm SATA/150
Mac Pro: 4 cores @ 3.0GHz, Mac OS X
Mac OS X 10.4.8; 2x 3.0GHz Intel Xeon 5160; 2,048MB DDR2 FB-SDRAM 667MHz; 512MB ATI Radeon X1900; 500GB Seagate 7,200rpm SATA/150
Mac Pro: 4 cores @ 3.0GHz, Windows XP
Windows XP Professional SP2; 2x 3.0GHz Intel Xeon 5160; 2.048MB DDR2 FB-SDRAM 667MHz; 512MB ATI Radeon X1900; 500GB Seagate 7,200rpm SATA/150
Mac Pro: 8 cores @ 2.66GHz, Mac OS X
Mac OS X 10.4.8; 2x 2.66GHz Intel Xeon 5355; 2,048MB DDR2 FB-SDRAM 667MHz; 512MB ATI Radeon X1900; 500GB Seagate 7,200rpm SATA/150
Mac Pro: 8 cores @ 2.66GHz, Windows XP
Windows XP Professional SP2; 2x 2.66GHz Intel Xeon 5355; 2,048MB DDR2 FB-SDRAM 667MHz; 512MB ATI Radeon X1900; 500GB Seagate 7,200rpm SATA/150
Related articles
Apple Mac Pro
Review Apple's Mac Pro has design innovations that we hope will cross over to other systems. Its performance is as strong as you'd expect for a system in its class, and it's priced right, too. You might need more flexibility in your configuration options, especially for 3D design. But otherwise, the Mac Pro is as solid a professional-class PC as we've seen. [21 Aug 2006]
Intel Core 2 Extreme QX6700
Review If you thought dual cores were over the top, get ready. Intel presents the Core 2 Extreme QX6700, a single CPU with four distinct processing cores. At $999, the first quad-core CPU will remain an enthusiast part for a while, but as a glimpse of the future, it's clear that clock speed is out and core counts are in. [02 Nov 2006]
Apple Boot Camp (beta)
Preview Apple gives the people what they want: Windows on Macs. Geeks proved it could be done through a variety of complicated hacks; now Apple has made it straightforward with a free download. We take Boot Camp for a test run. [10 Apr 2006]
Did you find this article useful?
273 out of 449 people found this useful
Full Talkback thread
2 comments
