That's funny, I'm noticing cooldowns across the board when using ML on my Mac Pro over Lion, although it's a Mac Pro 1,1. You might consider trying iStat Menus and using it to narrow down the problem, it gives you all the temps of the various locations in the Mac Pro. It will also let you adjust fan speed.
It's my fault for not being more precise. It's an early 2008 (3,1) Mac Pro with 3 Nvidia GT 120 cards. iStat is the tool I used to determine which areas/fans are running so high: it's the "Expansion Slots". Resetting the SMC was the first thing I tried, it did nothing (which is not unexpected since fan speed starts out normal after startup, then increasing to an uncomfortable 1600 RPM after about 20 minutes).
At this point I'm considering locating the temp sensor to stick a piece of gum on it or maybe disable it outright.
I'm a little ashamed to say that the other alternative is a downgrade to SL, which for the purposes of making peace with a once beloved OS I shall refer to as "The Good Old Times" from now on.
I would bet you anything it's those stupid GT120s. There is a reason you can't buy them from Apple anymore. They basically never made a decent Nvidia card. Or, wait for an ML graphics update. $20 says it will solve your problem.
The 4870/5870/6870 is a good choice if you're looking for something more compatible. The drivers for that series are steadily getting better and you can use the PC versions right out of the box with no modifications.
However if you have 3 GT120s for the reason I suspect, you need to power six displays or three dual DVI displays, then you're stuck.
Like I said it was fine on Lion and before. Fork over those 20 bucks ;)
I don't think there will be a graphics update for ML by the way. The MP (and whatever cards it uses) is an obsolete platform.
Thanks for suggesting alternative graphics, but I already upgraded from the previous gen ATI cards a few months ago and I'm not likely to buy more parts for this machine again. At this point I'm waiting what Apple does with the Pro and maybe buy a new one (or just leave Apple if they screw this product up too badly).
> Like I said it was fine on Lion and before. Fork over those 20 bucks ;)
Sorry I didn't mean there is a hardware problem with the cards, just that the hastily written ML GT120 drivers are most likely the culprit.
> I don't think there will be a graphics update for ML by the way.
Graphics updates are an expected part of an OS X release cycle at this point. We had one for SL, and Lion, and I would expect one for ML. Touchups across the board. What you're ignoring is that you already got a graphics update. By upgrading to ML, you're now on the 64-bit kernel and therefore are using the 64-bit kexts.
> The MP (and whatever cards it uses) is an obsolete platform.
Apple reaffirmed their commitment to the Pro line, so I wouldn't assume that so quickly. Also, behind the scenes evidence highly suggests that isn't the case. If Apple is planning to ditch the Mac Pro, they sure are steadily adding PC graphics card support for no explicable reason to OS X then.
Between 10.6.8 and 10.8.1 we've had support added for generic ATI cards and Nvidia cards of all stripes. Before 10.6.8, you simply couldn't boot a Mac Pro without an official card or card reflashed with EFI firmware.
Now, I haven't had an Apple official or reflashed card in my Mac Pro in a year and I use it every day, including right now. None of this has yet resulted in a product Apple actually sells. That bodes quite well for the future of the Pro line.
Make sure you reset the SMC too.