Exclusive: ZDNet overclocking tool enhances performance of Mac Pro

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Apple owners can do a lot of things better with their computers than Windows users can. Despite this, there are a few things that are easier to implement under Windows. These used to include overclocking. Many PCs can be overclocked in the BIOS set-up, although this does not apply to most brand name machines, such as those from Dell, HP or IBM. Under Windows, however, overclocking tools such as Clockgen, SysTool or CrystalCPUID can be used.

ZDNet Clock for the Mac Pro is easy to operate.

Macintosh computers lack a BIOS setup entirely – and Windows tools will not run under Mac OS. So ZDNet.de developed the overclocking tool "ZDNet Clock" for Mac OS X. The current version 1.0 supports only the Mac Pro and the Apple server Xserve. An Intel processor and the current operating system version, Mac OS X 10.5.x Leopard, are also required.

ZDNet uses three Mac Pros as test machines. One comes from the first Intel/Mac Pro generation (Mac Pro 1.1) with 65-nanometer processors and 1333-MHz front side bus. The others come from the third generation with 45-nanometer processors and 1600-MHz front side bus, as sold by Apple since January 2008 (Mac Pro 3.1). The first computer is equipped with two 2.66 GHz X5355 processors, and runs stable at 3.10 GHz, see figure 2. The other two have two 2.80 GHz E5462 processors. These can be overclocked up to 3.24 GHz and remain stable, see figure 1.

Entry-level model faster than the most expensive Mac Pro

The improvement in performance is quite remarkable. For example, the cheapest Mac Pro in the current series with a 2.80 GHz processor runs significantly faster after overclocking than the most expensive at 3.20 GHz. This is because in addition to the CPU frequency, the main memory clock speed is also increased, which results in an additional increase in speed. The price difference between these two machines is 1430 Euros.

ZDNet plays it safe when overclocking. ZDNet Clock does not use any voltage increase for the CPU, the front-side bus (FSB) or the memory modules. Voltage increase leads in increased electro-erosion and shortens the life of the modules in question. In order to designate an overclocking trial as stable in the ZDNet test, the computer has to perform the mprime torture test for 24 hours without any errors. And in addition to this, there must not be any reports of ECC errors from the FB-DIMM main memory modules.