Mac Book Pro, Part the Sixth
By Josh Simons on Feb 20, 2007
This weekend, my Mac Book Pro started making a new noise. Like a teapot whistling in the distance. Or someone screaming. Very noticeable and unpleasant. Given all of my previous problems I was going to ask Apple to consider giving me a replacement machine if they determined it needed yet another repair. As it turned out, the technician was able to fix this problem over the phone. Well, he made the problem go away. We'll see if it comes back.
He first had me reset the SMC (system management controller) by shutting down the system, removing the AC power, removing the battery, and then holding down the power button for 15 seconds. After reinserting the battery and reattaching the AC power, he had me reset the system's PRAM (parameter RAM) and NVRAM (nonvolatile RAM) by pressing the power button and then immediately holding down the Apple, Option, R and P keys until the 2nd reboot chime had sounded. The noise was gone once the machine rebooted.
Resetting the SMC also resets the PMU (power management unit), which had apparently lost its mind and needed a reset. Once the technician mentioned this, I recalled that the system did seem to be burning through its battery power faster than usual and I'd had occasional (and new) problems getting the system to sleep properly. Apparently, these are both also symptoms of a PMU that needs to be reset.