updated 10:05 am EST, Wed February 3, 2010
Spikes in power, heat
The current Nehalem-based version of the Mac Pro, released in October 2009, is being impacted by unusual performance problems, owners say. Certain audio tasks -- ranging from playing music in iTunes, to using USB or FireWire interfaces -- may cause performance to drop by as much as 20 percent in other areas. CPU power consumption can multiply by several orders and generate twice the normal amount of heat.
The problems are believed to be connected to Mac OS X, as booting into Windows 7 on a Mac Pro eliminates any issues. Based on testing it is suspected that there could be a flaw in OS X's handling of power management kernel extensions, or else the driver that exploits particular Nehalem features, such as SpeedStep and Turbo Boost. Apple has not commented publicly on the matter however, and so it is unclear where the precise fault lies.
AppleCare technicians are reported to have dismissed user complaints in a number of situations. The company should nevertheless be aware of audio issues, as one case is said to have been forwarded to engineers at Apple's Cupertino headquarters. Problems with iMacs may be taking a higher priority.