Monday, May 9, 2011

OSX Slow Boot / Can't Change Boot Volume

I recently had a very odd problem with my iMac. I have a after market SSD in it and have Boot Camp set up with Windows 7. It has been working fine for about a year now but all of the sudden my boot time tripped and I was no longer able to switch OS's with BootChamp nor set a startup volume in System Preferences.

After some investigation I found the following symptoms and error messages:
  • There were some scree rendering issues / I could mouse the mouse but not click or type.
  • I was able to use Remote Desktop / VNC to connect and interact with the computer properly.
  • In Activity Monitor the kernel_task process was using 100% of the CPU on one of the cores.
  • I could boot to Windows at startup and had no problems, errors, or lag there.
Could not find IODeviceTree:/options
EFI found at IODeviceTree:/efi Mount point for /Volumes/BOOTCAMP is /Volumes/BOOTCAMP
flushing fs disk buffer returned 0x5
IOHIDSystem: postEvent LLEventQueue overflow.
Can't access "efi-boot-device" NVRAM variable
no bootx creation request
nvram: nvram is not supported on this system

One of the messages when I was testing the Unix bless command indicated that the "efi-boot-device" NVRAM variable was not accessible. I then tried to examine it with the Unix nvram command only to get the "nvram: nvram is not supported on this system" error. I found the NVRAM error very odd And was surprised the computer was even booting if the nvram was defective. I then tried to reset the NVRAM as it was not operating properly.

As it turned out the problem all along was that the NVRAM had corrupted and was non-functional. I did a hard reset of the NVRAM and all the problems went away immediately. To reset the NVRAM you just reboot and hold down Command, Option, P, and R as the computer boots, or see this Apple Document.

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