When I tried to boot my Mac Pro recently, it failed -- all I got was a black screen and a chime. I opened the case, and on the motherboard, I saw two LEDs were red: the cpuA and cpuB failure lights.

My warranty is over, but here are the steps I followed to get it working again:
  1. Turn off your Mac and unplug the power cord.
  2. Remove the CMOS battery on the motherboard (just above the graphic card).
  3. Wait 10 seconds -- I'm not sure if this is necessary, but it worked for me.
  4. Plug the power cord back into the Mac.
  5. Press the power button. The Mac should boot normally and give you the startup chime, but you want your CMOS battery back.
  6. Turn off the Mac, then unplug the power cord again.
  7. Put the CMOS battery back in.
That's it; boot and enjoy!

[robg adds: I've never seen this on my Mac Pro, and I'm not sure if it's a sign of a failing CMOS battery, or something else. I'm publishing the hint beca...
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This entry was posted on Tuesday, August 26th, 2008 at 3:30 pm and is filed under News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.