4 Replies Latest reply: Nov 24, 2011 5:15 PM by Kurt Lang
Gerard James Level 1 Level 1 (5 points)

I thought that my 27-Inch iMac 2.66GHz Intel Core i5 ran in 64-bit mode by default but I see that it doesn't right now. When I go into the System Profiler and select "Software", I see:

 

64-bit Kernel and Extensions:    No

 

Yet, when I look in my Activity Monitor, I see Intel (64-bit) under "Kind" running for almost all the processes except for a couple. Is this ever royally confusing or what.

 

I use a couple of FireWire Interfaces for recording and would like to enable 64-bit mode for the extensions they use (for my M-Audio in particular).

 

How can I permanently enable 64-bit mode? I could swear that before I updated from 10.6.6 to 10.6.8 a few days ago that I was running in 64-bit mode. Also, does enabling 64-bit mode have any effect on Rosetta?

 

Is there any disadvantage to running in 64-bit mode (ie: will certain things not work)?

 

Thanks in advance.


27-Inch iMac 2.66GHz Intel Core i5, Mac OS X (10.6.8), 8 GB RAM
  • QuickTimeKirk Level 9 Level 9 (50,550 points)

    How much RAM is installed on your machine?

  • Kurt Lang Level 7 Level 7 (34,835 points)

    Your Mac should certainly be able to boot 64 bit. Just to test, restart and hold down the 6 and 4 keys. Then check the System Profiler to see if the 64-bit Kernel and Extensions says "Yes".

    Yet, when I look in my Activity Monitor, I see Intel (64-bit) under "Kind" running for almost all the processes except for a couple.

    That's normal. The kernel can boot 32 or 64 bit. But all 64 bit software, system or third party, can still run 64 bit under a 32 bit kernel.

    Also, does enabling 64-bit mode have any effect on Rosetta?

    No.

    Is there any disadvantage to running in 64-bit mode (ie: will certain things not work)?

    Not really. The only real issue is drivers that must load during startup. If they're 32 bit only, they won't load if you start up to a 64 bit kernel. You would then be unable to use the device the driver is for.

     

    Here's the configuration file approach for always booting into 64-bit. This is the best way to make your Mac always start up 64 bit as the only thing necessary is to alter one line of a configuration file. You can do that by opening the Terminal and entering (or copy the next line and paste in into Terminal):

     

    sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' 'arch=x86_64'

     

    To return to 32 bit mode, you would repeat the command but enter an empty string, which would just be the single quotes (where arch=x86_64 is in the above command) with nothing in between.

     

    sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' ''

     

    The forums wrap these commands to fit the box, but if you copy/paste it, they will be one line.

  • Gerard James Level 1 Level 1 (5 points)

    Wow, thanks for the great answers! I will do this and stay in 64-bit mode. I have 8 GB of RAM with 16 coming the morning of December 25th (provided I've been a good boy)

  • Kurt Lang Level 7 Level 7 (34,835 points)

    You're welcome, Gerard. A small note, you don't have to enter the second Terminal command to get the Mac to boot 32 bit if you need to. Holding down the 3 and 2 keys during startup will still override the configuration's setting of 64 bit.