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10.6: How to boot into the 64-bit kernel System 10.6
Users who want to run the new 64-bit kernel on late-model Macs (pretty much anything released after early 2008) can do so by booting with the 6 and 4 keys held down. If you're wondering whether your Mac has a 64-bit EFI firmware, you can type this command in Terminal:
ioreg -l -p IODeviceTree | grep firmware-abi
The response will identify the machine as either having 32-bit or 64-bit EFI. I found this tidbit in this article on AppleInsider.

[robg adds: Note that if you boot in 64-bit kernel mode, you may have unexpected oddities. In my case, web pages that contained Flash animations would cause Firefox to quit. Rebooting in 32-bit mode (hold 3 and 2 during boot) solved the problem. Unless you have a definitive need for the 64-bit kernel, I'd recommend sticking with 32-bit mode for now.]
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10.6: How to boot into the 64-bit kernel | 24 comments | Create New Account
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10.6: How to boot into the 64-bit kernel
Authored by: freecris on Sep 15, '09 08:16:31AM

Hi,

you don't need to press "3" and "2" to boot in 32bit, just reboot without press any key.

i use firefox 3.5 with flash. no problem in 64bit.



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10.6: How to boot into the 64-bit kernel
Authored by: robg on Sep 15, '09 10:48:17AM
The following page crashed *every* browser on my MacBook Pro when running in 64-bit kernel mode:

French spiderman scales Malaysias Petronas Towers

-rob.

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10.6: How to boot into the 64-bit kernel
Authored by: Felix on Sep 16, '09 01:14:41AM

@robg "The following page crashed *every* browser on my MacBook Pro when running in 64-bit kernel mode: "

I just tried your link to the French spiderman story, Rob, and read the page and played the video with no problems.

System Profiler, System Software Overview reports "64-bit Kernel and Extensions: Yes

MacBookPro5,1
Mac OS X 10.6.1 (10B504)
Safari 4.0.3

I booted this MBP into 64-bit mode several days ago and haven't had to go back to 32-bit mode yet. Guess I don't have many plug-ins or extensions requiring the underlying applications to be running in 32-bit mode.

Unlike your guidance, I'd suggest people try 64-bit mode to find out whether it's problematic for them personally or not. As I'm sure you know, on a 64-bit processor a 64-bit kernel can run both 32- and 64-bit apps (but a 64-bit kernel can load only 64-bit kexts or kernel extensions).



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10.6: How to boot into the 64-bit kernel
Authored by: DEMON on Sep 15, '09 08:29:14AM

Not all macs with a 64bit EFI can boot in the 64 bit kernel mode, because the DIMM (memory) is still 32 bit.

Only if all the hardware is 64 bit your mac will be fully 64 bit capable.



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10.6: How to boot into the 64-bit kernel
Authored by: outZider on Sep 15, '09 10:40:08AM

Uh, no. This has everything to do with firmware and drivers. If you have a 64 bit capable processor, you're theoretically fine as soon as Apple supports you. 64 bit matters in how you address the memory, not what the memory "is".

This is exactly why you can install 64 bit Windows, 64 bit Linux, 64 bit FreeBSD, and 64 bit Solaris on any other 64 bit capable Intel processor, and even those Macs that don't have 64 bit OS X support yet.



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10.6: How to boot into the 64-bit kernel
Authored by: David Allen on Sep 15, '09 08:31:19AM
(pretty much anything released after early 2008) can do so
Not so. 64-bit chip + 64-bit EFI ≠ 64-bit mode. The list is a bit restricted. Basically '08 & '09 iMacs, '08 &'09 MacBook Pros and '08 & '09 Mac Pros and '08 & '08 xserves can boot into 64-bit mode. Brand new Mac minis and PowerBooks have both the chip and the EFI, but Apple does not grant them the kernel and they cannot boot into 64-bit mode.

---
David Austin Allen
Monterrey, NL, MX

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10.6: How to boot into the 64-bit kernel
Authored by: iandol on Sep 15, '09 03:09:58PM

Indeed, Apple have failed to port the drivers for their hardware for a number of their recent Macs. I find it amazing that they are unable to support their own hardware properly by rewriting their own kernel extensions for the limited pool of hardware they use...



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10.6: How to boot into the 64-bit kernel
Authored by: thyvillageidiot on Sep 15, '09 10:16:48AM

Any advantage for the average user (in iTunes, iMovie, Safari, etc.?)?



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10.6: How to boot into the 64-bit kernel
Authored by: tim1724 on Sep 15, '09 02:51:26PM

No advantage at all, at least not yet.

The only cases where a 64-bit kernel makes much of a difference is if you have lots of RAM (and by lots I mean 20 GB, not 4 GB) or if you have device drivers which need to map a ton of address space (very rare now, but will be more common in a few years)

In 3 years or so you'll want to have a 64-bit kernel, but it's not necessary right now. And there is one big downside right now: most third-party kernel extensions (including many device drivers) are only available for the 32-bit kernel.

---
Tim Buchheim



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10.6: How to boot into the 64-bit kernel
Authored by: frgough on Sep 16, '09 07:17:12AM

Not entirely true.

Because of the Intel architecture, 64-bit programs (including the kernel) gain access to more registers, which translates into a speed increase.



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10.6: How to boot into the 64-bit kernel
Authored by: The Eck on Sep 15, '09 01:26:14PM

How does one find out whether the machine has booted into 64 bit? I tried looking at the system profiler but couldn't find anything. Nothing showed up during the boot (like when you do a safe boot).

Thanks!



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10.6: How to boot into the 64-bit kernel
Authored by: jeremyp on Sep 15, '09 02:11:37PM

Open Activity Monitor and look for a process called kernel_task. The "kind" column will be either intel or intel (64 bit).



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10.6: How to boot into the 64-bit kernel
Authored by: blgrace on Sep 15, '09 10:55:49PM

Also, in System Profiler - just click on the word "Software" in the Contents column.
That will tell you if you're running 64 or 32



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10.6: How to boot into the 64-bit kernel
Authored by: jabba on Sep 16, '09 02:30:35AM

To find out your currently running kernel, you can open up Terminal.app and type in "uname -r" or "uname -a" without the quotes, if you are in 32-bit kernel, there will be something like i386 in the output. I haven't tried 64-bit mode, but it would likely say something like x86_64 or something similar instead.



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10.6: How to boot into the 64-bit kernel
Authored by: mchagers on Sep 16, '09 01:59:16PM

Or you can just open the System Profiler and click on the Software Category.
If it says on the second line from below:
64-bit Kernel and Extensions: Yes
You're running in 64-bit I assume.



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10.6: How to boot into the 64-bit kernel-VMWare Fusion
Authored by: dave@mmu on Sep 16, '09 01:14:15AM

Hiya guys/gals, one other thing to watch out for is software incompatibility. VMWare Fusion will not run when booted in 64bit mode for example which is a pain. In 64bit kernel mode on my latest Macbook Pro with 4Gb RAM i didn't really see any difference but that was under 10.6.0 and not .1 so maybe it's different now.

---
Dave L



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10.6: How to boot into the 64-bit kernel
Authored by: macgruder on Sep 16, '09 01:35:49AM

This is an interesting hint. People who are not really really sure of its implications should ignore it though :-)

Whether you boot into the 64-bit <b>kernel</b> or not, your 64-bit <b>apps</b> and libraries will still run in 64-bit.

So stick with the 32-bit kernel unless you are sure that all of your kexts are fine with the 64-bit kernel, and you need massive amounts of memory - dozens of gigs.

The only other reason for booting into the 64-bit kernel that I can think of is if you are the kind of person who enjoys saying my **** is bigger than yours :-)



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10.6: How to boot into the 64-bit kernel
Authored by: frgough on Sep 16, '09 07:20:13AM

Again,

Because of the Intel architecture, 64-bit processes gain access to more registers and will experience a speed increase.



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10.6: How to boot into the 64-bit kernel
Authored by: macgruder on Sep 17, '09 07:49:56AM
Yes, but all users will get this speed increase for their 64-bit apps whether or not they boot into the 64-bit kernel. For the vast majority of users the kernel running in 64-bit will not make a noticeable difference - but they may well run into compatibility problems.

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10.6: How to boot into the 64-bit kernel
Authored by: Crazor on Sep 16, '09 04:41:16AM
If your Mac hardware is capable, but Apple doesn't want you to run K64, there is a way to patch the boot.efi: http://www.osxbook.com/blog/2009/08/31/is-your-machine-good-enough-for-snow-leopard-k64/

With this patch, I'm able to run K64 on my late 2008 unibody MacBook just fine, no problems yet. Note that while Amit Singh lists the offsets for other models than the MacBook, he hasn't tested them yet (and me neither).

I used HexEdit for the patching (remember selecting and then overwriting the byte, inserting a byte will damage the file). If you don't want to patch the offsets yourself, there's a ready-made boot.efi here: http://netkas.org/?p=189
Note: either did netkas only patch the location for MacBooks or the patch as described by Amit Singh does not work on other Macs. At least that is what I read from netkas' post.

Maybe this should be run as a hint on it's own...

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10.6: How to boot into the 64-bit kernel
Authored by: efseiler on Feb 27, '10 02:30:00PM

This link explains very clearly how to boot recent Intel Macs in full 64-bit mode:

http://antihackerlink.or.id/kernel-64-efi-patch-os-x-10-2-6.html

I can attest that it works for my Early 2009 Mac.

I'm skeptical that booting in this mode would cause compatibility issues as every single kernel extension is 64-bit.

--Damien



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10.6: How to boot into the 64-bit kernel
Authored by: efseiler on Mar 01, '10 12:12:30PM

I might add that according to the system log the only kernel extension not supported is 'InternalModemSupport.kext'

Apparently it contains no code for running the kernel's architecture.


I would guess that Apple disables booting the 64-bit kernel in the low-end Intel macs so as to create an additional valid selling point for the high-end macs where booting into the 64-bit kernel is enabled by default.


--Damien



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10.6: How to boot into the 64-bit kernel
Authored by: efseiler on Mar 02, '10 07:06:52AM

One last thing I noticed about using the 64-bit kernel is the cooler operation. When running the mini at full bore (in this instance recompiling a complex port) the core temperature never rose above 175F whereas when using the i386 kernel the core temperature would frequently rise above 200F!

--Damien

Edited on Mar 02, '10 07:08:11AM by efseiler



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10.6: How to boot into the 64-bit kernel
Authored by: efseiler on Mar 05, '10 07:28:24AM

As a final note...according to Wikipedia:

"K64 has several benefits compared to K32:
Can manage more than 32 GB RAM, as the memory map would consume a disproportionately large area of the 32-bit kernel space.
Cache buffer sizes can be larger than what the 32-bit kernel space allows, potentially increasing I/O performance.
Performance is increased when using high-performance networking devices or multiple GPUs, as the kernel can map all of the devices in 64-bit space even if several have very large DMA buffers.
Booting while holding down 6 and 4 will force the machine to boot K64 on machines supporting 64-bit kernels. K64 will run 32-bit applications but it will not run 32-bit kernel extensions (KEXTs) so these must be ported to K64 to be able to load."



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