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Is Mountain Lion too hot for your Mac to handle?

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With every major upgrade of Apple’s OS X(s AAPL), there will be questions: When should I upgrade, why should I upgrade, will the upgrade work for me?  Apple has done its best at eliminating most of the headaches that previously plagued the upgrade process: the cost is only $20, the software downloads and installs directly from the App Store and the migration assistant will move your apps, user settings and data for you.  And thankfully there are many early adopters out there that have already blogged about their experiences with the latest upgrade to OS X Mountain Lion over the last few months.  But now it’s your turn. Here are three questions– and answers — that should help identify if your Mac is prepared for the Mountain Lion upgrade.

Which Mac do you own?

One of the great things about Apple’s products is that they last a long time.  Unfortunately they tend to outlast the support of the version of OS X they originally shipped with. With each major release of OS X, you need to check and see if your Mac is eligible for the upgrade.  To install Mountain Lion on your Mac will need to have a 64-Bit Intel Core 2 Duo processor and an advanced GPU chipset, like the Intel GMA 950 or x3100 or the ATI Radeon X1600 graphics. To figure out if your Mac qualifies, you need to figure out the exact model of your Mac.  This can be done by checking More Info on the About This Mac item from the Apple menu.  Here you will find your Mac’s serial number.  Use the serial number on Apple’s Tech Specs website to see which Mac model you have and the system requirements for Mountain Lion.

This chart summarizes the requirements:

Supported Hardware

Just because your Mac made the cut and can install Mountain Lion, however, does not necessarily mean that you will be able to run all of the new features included with Mountain Lion or even its predecessor Lion.  These so called “in-between Macs will install and run most of the new features of Mountain Lion, but not all of them.  The first such feature is AirDrop. This is the wireless file sharing feature that was introduced in Lion. Your Mac needs a specific Airport Express card installed that only started shipping on Macs late in 2008.  The chart above indicates which Macs do support AirDrop.

The second major feature that these “in-between” Macs will not support is AirPlay Mirroring, This feature will allow you to use your HDTV as an external monitor wirelessly through an Apple TV, the way you already can with your iPhone or iPad.   It’s not clear why AirPlay Mirroring won’t work on certain Macs. Some have speculated that this is a DRM-related issue, others that it is tied to the kind of GPU a machine has, and some that it is related to network bandwidth of the Airport card installed.  Regardless of the real reason, if your Mac is older than 2011, then it will likely not be able to stream its screen onto your HDTV via an Apple TV.

Will your old apps still work?

If you are upgrading from an older version of OS X on your current Mac, or if have finally decided that it is time to upgrade your hardware, you may want to check and see if all of your favorite apps will still run on Mountain Lion.  OS X Tiger was the first version of OS X that ran on both Intel(s INTC) processors and IBM’s PowerPC(s IBM) processors.  With this dual chipset support came a convenient technology called Rosetta that kept your PowerPC apps running even if you were running an Intel-based Mac.  With OS X Snow Leopard, you had to manually add Rosetta, and with Lion Rosetta was not supported at all.  Apple decided to no longer support any application that was built for the older Macs running on the PowerPC architecture.  This is a good thing for OS X, as Apple has chosen to make a clean break from the past and focus on optimizing its OS on the current Intel chipset.  And like Lion, it should be no surprise that Mountain Lion does not support Rosetta either.

Application Kind

To check to see if your Mac is still running any old PowerPC apps, look again at the More Info on the About This Mac item from the Apple menu.  Look under the Applications list located under Software.  Here you will see a list of installed applications and their associated Kind, and there which work with PowerPC-based Macs.  These are the applications that will not run on either Lion or Mountain Lion.  Also with last summer’s introduction of Lion, you had to manually install third-party some software that used to come pre-installed on older Macs, most notably Java Runtime for OS X and Flash plugin for Safari.


What is new with Mountain Lion is a security technology called Gatekeeper.  Gatekeeper can block apps from being installed if they are not purchased from the Mac App Store, or if the developer did not register with Apple and get a special Developer ID for their application.  The default setting will be to only allow apps to launch if they have been downloaded from the Mac App Store or apps that have this new Developer ID.  You can, of course, turn this security feature off to allow the installation of any application.

How hot is too hot for a CPU?

Anytime your Mac starts getting a little hot, you should try to understand why.  This is particularly noticeable when your MacBook is resting on your lap.  During the upgrade process to Mountain Lion, and for a short time thereafter, most Macs will runs little hot.  I know this because this also happened to me when upgrading from Snow Leopard to Lion.  For the most part this is normal.  If you check your list of running processes, you will find that it is Spotlight that is eating up all of the CPU’s time and causing things to get a little hot.  (Spotlight is the feature that allows you to find all of your files quickly and easily on your Mac.) With each major upgrade, Spotlight will re-index all of your files.  This process could take some time depending on how many drives you have attached, and how many files are on those drives.  The following are temperatures that I noticed when upgrading various Macs.

Mac Temperature

Depending on how old your Mac is, you may see a slight rise in the average temperatures of your Mac even after Spotlight has finished.  Newer Macs will typically return to the same average temperatures prior to the upgrade.  This makes sense as there are some additional process running in the background to keep all of the new iCloud services in sync.  But what if things start to get really hot?  Intel chips have a built-in feature called THERMTRIP that will temporarily suspend the CPU when things get hot, and shut down the CPU altogether when things get too hot. Speculation is that this temperature is somewhere in the neighborhood of 120-130ºC.

Control the Heat

If you want to keep tabs on your Mac following the upgrade, consider installing iSlayer’s iStat Pro, which will allow you to monitor several of your Macs’ vital statistics including temperature.  There is even an optional iOS app from Bjango that acts as a client to iStat Pro.  With it you can monitor your Mac from your iPhone when you’re on the same Wi-Fi network.  And when things seem to get a little too hot, you can manually modify the speed of your internal fans by installing Hendrik Holtmann’s smcFanControl.

Four years running on five

For the most part, upgrading to Mountain Lion will be an easy process and bring with it many new features and security patches.  Staying current does tend to result in hardware upgrades, but the list of model years that Apple is supporting is quite long.  I have been running a mid-2008 MacBook Pro with Mountain Lion for some time now, and it has been performing just fine.  In fact, I have found Safari’s performance to be much improved on this four-year-old Mac.  Granted, things are running a little bit hotter since I first got the Mac back in 2008, but it is not uncomfortably hot.  And I will just have to learn to live without AirDrop and AirPlay Mirroring until I decide to upgrade my hardware.

30 Responses to “Is Mountain Lion too hot for your Mac to handle?”

  1. It will not run on my Late ’08 MBP. All kinds of tries: external drive, other ML MBP in Terminal mode, Clean installs tried too. It just will not fully boot up. (Nor will Lion 10.7.5.) But Lion 10.7.4 is very stable. A mystery!

  2. Thank you for including a number or two to help us quantify “hot”! I actually nearly had a shouting match with an Apple rep today, because she kept quoting me the “operating temperature” (50-95, roughly) as if it told me the safe temp of my system itself. I have a utility called DiskDrill, which is reporting 104F for my SSHD and 134F for my regular HD, and nobody at Apple is able to tell me whether or not this is a problem. They just want me to shlep my 17″ iMac to an Apple store, where they will run some standard tests and see if it “feels too hot.” Really? Have you any advice on this?

  3. Late last year I bought an iMac 27″ which came with Snow Leopard operating system. I has been a great computer experience from my all the window based I’ve had in the past. My concern is that even thou I want to get the new upgrades…I’m scare to slow my system down!! Is there any assurance this will not happen!!


  4. Mike Halloran

    Definitely not the hard drive. Using Temperature, I am able to determine that my CPUs are running about 20 degrees F hotter. The temp difference for my internal drive is less than 2 degrees.

    I have a 2010 27″ iMac with the OWC eSATA mod. Running Lion on my internal drive and ML on a clean external via eSATA. I switch back and forth between the two and save the temperature reports to .pdf.

    • It actually turns out to be the hard drives in the older models that seem to be the issue. My 2006 MacBook is running mountain lion like a pro. I upgraded my hard drive to a 1Tb recently and now my MacBook reads as a late model 2009 in the “about this Mac” section and runs mountain lion OS X wonderfully. Trying to spread the word in case people want to upgrade.

      • Funnily enough both my 2007 iMac and 2008 Aluminium unibody Macbook (not pro) have both had hard drive upgrades and are running Mountain Lion Flalwlessley

  5. Bleh I have an early 2008 White Macbook, and guess I can’t get this upgrade. Something bout while the CPU can handle 64bit, the EFI cannot.

    • I am posting where ever I can to let people know. It actually seems to be the hard drive that’s the issue. I have a 2006 MacBook and am currently running Mountain Lion. I recently upgraded to a 1TB hard drive and now my MacBook reads as a late model 2009 and runs Mountain Lion great! Hope this helps!

    • It actually turns out to be the hard drives in the older models that seem to be the issue. My 2006 MacBook is running mountain lion like a pro. I upgraded my hard drive to a 1Tb recently and now my MacBook reads as a late model 2009 in the “about this Mac” section and runs mountain lion OS X wonderfully. Trying to spread the word in case people want to upgrade.

      • Nicholas

        i have n early 2008 macbook with a recently upgraded 500g hard drive – when i try to download mountain lion the server responds that it iis not compatible with this computer did those of you who have this running have the same issue and is there a way around it?
        thanks nic

  6. Daniel

    I was planning on upgrading my late 2008 core 2 duo macbook pro 2.4ghz to Mountain Lion, but now I’m thinking that it will slow down my computer (particularly concerned with photo editing), the last thing I’d want. Am I right to think that? I’d like to stay current, but not at that cost.

  7. Richard Rumrill

    Think you have the mb pro and air airplay mixed up on the chart. Apple says early 2011 (not mid) will support new airplay features. Had me real scared there!

  8. “The following are temperatures that I noticed when upgrading various Macs.”

    To replicate your readings, we need to know on which part of the computer you measured them.

    • I was looking at the temperature displayed by smcFanControl on the menu bar which did not require me to launch dashboard. It is the CPU temperature and matches the CPU temperature value being measured by the dashboard widget iStat Pro. Measurements were observations during periods of little to no activity being conducted but the user, and no applications were open at the time of the observation. Temperatures were noted in degrees celsius.