Wake From Sleep Fan Noise Mac Pro 2.66

This is now normal since one of the previous firmware updates.

There was much debate over the reasons. We don't know the true one, but the general assumption is that it prevents heat build-up during sleep from continuing by venting it out as soon as the computer awakes. You can make up your own reason if you wish.

90 seconds though ?!
I get that for maybe 10 seconds.... ?!

Happened yesterday, first time in over a month.

The fans should respond to sensors, which should pick up temperature changes, but yes, seem to be slow to respond.

However a system sleeping isn't dispelling heat efficiently.

Some 3rd party RAM could be faulty or hot, and some tend to stay cooler and better at radiating heat away.

If you have the pre-2008 you can press the smc_rst button and zap pram/nvram, that along with running smcfancontrol 2.1.2 (www.macupdate.com is best place to find) to keep the fans revving higher.

More RAM = more heat. And it wasn't until March '07 or later that memory for Mac Pro was really 'perfect-ed' to the point it ran cooler and less errors.

Not everyone has the same ambient room temps, configuration of drives, and other factors.

Most people did or have since Sept '07's SMC Update, had this, which was to correct a much more critical problem, not keeping the system cool enough.

There are some extensions in OS X that have filenames of SMC, SMU, PMU etc though I don't know what they do. Some settings are stored in NVRAM too.

3rd party RAM alone is not the cause, though the quality or mix might. I have three makes of memory in mine. And even Apple's own OEM memory has been the cause at least a few times on this forum.

FWIW,
I've had 4 1GB since I purchased the machine and have always had this problem, even before the firmware update that was supposed to address fan issues.