Sleep issues or a kernel panic may occur if a storage device is mounted via a PCI card that doesn‘t support sleep

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Issue or symptom

Issues may occur when waking the computer from sleep if a storage device is connected to a PCI or PCI/e card that doesn't support sleep, and its volume is mounted in the Finder:

  • The computer may not wake
  • A kernel panic may appear
  • The computer may wake, but this alert message may appear, and the connected storage device will no longer be available (mounted):

"Device Removal
The device you removed was not properly put away. Data might have been lost or damaged. Before you unplug your device, you must first select its icon in the Finder and choose Eject from the File menu."

Products affected

  • Desktop Macs with PCI/e expansion slots (such as Power Mac G4, Power Mac G5, and Mac Pro computers)
  • PCI expansion cards with USB 2.0 ports
  • PCI expansion cards with FireWire ports


Connect the storage device(s) to your Mac's built-in USB or FireWire port instead of through a PCI card. The internal bus should retain a physical connection to the device during sleep, as long as the device is FireWire/USB 2.0-compliant.

You should not connect storage devices--such as USB drives or FireWire drives, memory card readers, and other storage devices that are mounted as volumes in Finder--to PCI cards, unless the card is designed to prevent the computer from sleeping. PCI bus power is normally turned off in sleep mode; storage devices will be disconnected from Finder when this occurs, which may prevent the Mac from waking from sleep for several minutes (or at all).

Alternatively, you can use Energy Saver preferences in System Preferences to disable computer sleep. Move the "Put the computer to sleep when it is inactive for" slider to "Never". However, this would not prevent the computer from attempting to sleep if Sleep were chosen from the Apple menu.

Note: This issue does not affect devices such as printers, scanners, and other non-storage device because they do not "mount" in Finder. These devices re-enumerate when the computer wakes up. Some printers include media card readers, which may appear in the Finder as a storage volume. If the printer is connected to a PCI expansion card's USB or FireWire port, and the is card media mounted in Finder, the media's volume will be unmounted when the computer sleeps.

Additional information

Peripheral Component Interconnect (PCI) or PCI Express (PCI/e) cards allow you to customize your Mac for the special needs of your workflow. Adding PCI or PCIe cards can provide additional power and productivity by means of video cards, video management, RAID controllers, network cards, or more.


Related documents


303698 Mac OS X: Why your Mac might not sleep or stay in sleep mode
86400 Mac OS X: Apple Fibre Channel and SCSI PCI Card Can Prevent Deep Sleep



Published Date: Feb 20, 2012