Mac OS X v10.6: Starting up with the 32-bit or ...

Summary

Mac OS X v10.6 Snow Leopard includes a 64-bit kernel. On hardware that supports the 64-bit kernel, you can choose whether to start up (boot) your Mac using the new 64-bit kernel or the earlier 32-bit kernel.

Products Affected

Mac OS X Server 10.6, Mac OS X 10.6, Mac Pro (Mid 2010)

You can use either of these methods:

Method 1: Startup key combination (for current startup only)

• If your Mac uses the 32-bit kernel by default, but supports the 64-bit kernel, you can start up using the 64-bit kernel by holding the 6 and 4 keys during startup.
• If your Mac uses the 64-bit kernel by default, you can start up with the 32-bit kernel by holding the 3 and 2 keys during startup.

Your Mac will revert to the default kernel the next time you reboot it.
 

Method 2: On-disk setting (persistent)

To select the 64-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture x86_64

To select the 32-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture i386

Note: This setting is stored in the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file and will take effect every time you start up from this disk. If you start up from a different disk, the setting on that disk, or the hardware default, will take effect.

Additional Information

• Keys held during startup (such as 3-2 or 6-4, method 1 above) will override the setting in com.apple.Boot.plist (method 2 above).

Note: Learn how to determine whether your Mac can use the 64-bit kernel and which kernel it uses by default.

 

 

 

打开 /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
把
<key>Kernel Flags</key>
<string></string>
替换成
<key>Kernel Flags</key>
<string>arch=x86_64</string>


切换 32位 or 64位内核 – Mac OS X 10.6

Mac OS X颇有意思，安装的时候已经同时装了32位内核和64位内核，但对于非server版的10.6来讲，默认启动的是32位内核。Apple官方给出了如何快速切换内核的方法[1]：

1. 临时切换内核：

该方法只生效一次，下次启动又恢复成默认内核（方法2能够修改默认启动内核）：

启动时:

1) 按住 '3' 和 '2'，则本次启动进入32位内核；

2) 按住 '6' 和 '4' ，则本次启动进入64位内核。

2. 设置默认启动内核：

To select the 64-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture x86_64

To select the 32-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture i386

Note: This setting is stored in the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file and will take effect every time you start up from this disk. If you start up from a different disk, the setting on that disk, or the hardware default, will take effect.