Most PCs enable overclocking through the BIOS. Not so ZDNet Clock: The tool increases the bus clock speed, and thus also the frequency of the memory, only after the operating system has been started. The disadvantage of the former method with many motherboards is that a jumper has to be set if you have overclocked excessively. When overclocking by means of a tool, all it takes after a crash is to switch the computer off and on again. So it would seem that overclocking with a utility is the better option. The problem with the incorrectly running system clock demonstrates that this is not the case under Mac OS.
Safe overclocking with the Mac Pro
On the other hand, one problem that makes overclocking risky on most other computers, namely memory errors, does not occur in the Mac Pro. If you overclock a computer whose main memory does not have error correction, switching the frequency can lead to some serious malfunctions. If the memory errors, which always occur shortly after setting the new frequency, affect a few bits that contain, for example, the code of the file system driver, the result may be the complete loss of hard disk data. If, on the other hand, the computer is overclocked into RAM with the aid of the BIOS before loading the operating system and before shadowing the BIOS, this risk is eliminated.
As the Mac Pro has memory with error correction, overclocking after loading the operating system can do little damage. Either the errors are corrected or the kernel causes a controlled crash. For safety’s sake a stability test should be carried out with mprime after overclocking. As a rule, the memory does in fact drop out before the CPU, but you can play it safe if the stability test compares calculated results with previously known results. The best overclocking results are achieved with ZDNet Clock for the Mac Pro if the machine is equipped with brand-name memory. If you think, modules are overpriced, you should use branded memory such as by Kingston or Transcend. In contrast, the no-name modules also used in the test permit only minimal overclocking.