The Mac Pro has always been a beast of a computer, and even the first-generation examples remain so. Their reliability is second to none amongst the Apple product line, but with some approaching three years old we are beginning to see more failures. This week’s repair is on an 8-core 3.0 GHz unit outfitted with a Fibre Channel card normally connected to an Xserve RAID, 16GB of RAM, a super high-end Kona video card, and four 2TB hard drives set up in RAID 5.
Needless to say, this is a computer our customer desperately needed back up and running as fast as possible.
Because he bought AppleCare and the computer from Small Dog, he enjoyed a free loaner computer during the repair. But because we need the entire machine—fibre channel card, RAM, and all the hard drives—to properly diagnose, he had to make do with a more-or-less stock Mac Pro.
The Mac Pro came in for random kernel panics during time machine backups of the startup partition to a FireWire 800 LaCie external drive. First step was to swap the the RAM with known-good chips, and the kernel panics persisted. We then booted the computer from an external drive with a known-good operating system, and the kernel panics persisted. Then, the internal drives were unplugged and the machine booted again off the external drive. No luck.
Component isolation is where you strip a computer down to its minimal configuration and unplug every nonessential component; then plug them back in one-by-one until the problem reappears. When it does, you can be fairly certain the component just reinstalled is the culprit. In its minimal state and not showing symptoms, the optical drives were plugged in one by one with no luck. It can only be called good luck that the second component swapped in, the Bluetooth card, brought the kernel panics back. Swapping in a good one fixed the problem.
This was an easy one, but some of the harder Mac Pro diagnoses can take a very long time and are often a combination of software and hardware. More common failures are of hard drives, processors, logic boards, RAM, and RAM riser cards. Logic boards and processors are very expensive, so this customer was very lucky!