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Sleep vs. Doze on Mac OS X

Q: Is there any difference between sleep and doze on a Macintosh desktop computer running OS X?

A: Yes, sleep uses less power than doze. Sleep shuts down the CPU and the entire PCI Domain per the PCI Supplement. This includes the PCI slots on the motherboard.

In doze we leave PCI devices, the PCI bus, and the CPU powered on. Doze only occurs on systems that have PCI cards whose drivers aren't power managed. Doze also occurs on any machine that doesn't support sleep, like Apple's original PowerMac G3 computers. If you put a non-power managed PCI card into a recent PowerMac computer you might notice that it no longer goes into full sleep, just doze. The reason for doze is simple, a PCI driver that doesn't support sleep can easily panic a machine by trying to access PCI registers after the PCI bridge is powered down.

In sleep all devices are shut off. All portables and most desktops support sleep. As long as your driver supports power management (by calling PMinit and registerPowerDriver ) the machine will continue to sleep.

To learn more check out our Power Management DDK 1.0 Mac OS X .

[Oct 09, 2003]

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