R Blog

I’ve been tied up with this desire to run my Mac with 64-bit mode. First, I thought Snow Leopard is running on 64-bit kernel by default but I was wrong. Even though Snow Leopard has the ability to run on 64-bit mode, it doesn’t. The reason was to avoid hardware drivers and apps compatibility issues. But, unlike Windows Operation Systems, Snow Leopard can use all of my 4GB of installed RAM and most of the Snow Leopard’s System Apps are running with 64-bit mode. But still, I wanna try what it what it looks like to be in 64-bit mode.

So, first of all, I found this useful article about determining what kernel mode are you running and how to change vice-versa. Hit the read more button to find how to make your Mac to be booted into 64-bit environment!

Note. Some of your devices and Apps may not work in 64-bit mode. You’ve been warned and I assume you know what you are doing starting from this point and I shall not take any responsibilities should your system may become unstable or crash.

First, you can check what mode are you in by going to System Profiler > Software and check “64-bit Kernel and Extensions”. If it says No means you are in 32-bit mode.

Second, fire up the Terminal (Applications > Utilities > Terminal) and type or copy & paste the following code into the terminal and hit return.

ioreg -l -p IODeviceTree | grep firmware-abi

Your terminal would return either firmware-abit is “EFI64 or “EFI32″. If your old Mac says “EFI32″ then I’m sorry, you are out of this game. Your Mac won’t support 64-bit mode.

Boot Options

There are several ways to boot into 64-bit mode.

6-4 Keys

This is the quickest way to boot into 64-bit. Just press 6 and 4 on the keyboard at the start up after gray screen and before Apple logo. This method doesn’t change any system files or whatsoever so if you are just looking to test out the 64-bit, this is the best way to do so. Once you restarted the system, it will automatically goes back to default mode which is 32-bit.

com.apple.Boot.plist

But if you want your Mac to be booted into 64-bit every time it boots, you can edit this com.apple.Boot.plist in /Library/Preferences/SystemConfiguration/com.apple.Boot.plist. Add arch=x86_64 in string value shown as below.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Kernel</key>
	<string>mach_kernel</string>
	<key>Kernel Flags</key>
	<string>arch=x86_64</string>
</dict>
</plist>

The PRAM injection mode

If you find the above method is a bit hassle, you can try this one. Open Terminal again and type sudo nvram boot-args="arch=x86_64" and hit return. This will change the boot option to 64-bit mode. You can revert it back by just inject like this sudo nvram boot-args="".

That’s all we have to do to step up the system to the next step. I shall test out and run some benchmarks to see is it feasible to use 64-bit mode.

Ref. Macintosh Performance Guide: Mac OS X Snow Leopard – Booting into 64-bit Mode