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.

[ Reply to This | # ]

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

French spiderman scales Malaysias Petronas Towers

-rob.

[ Reply to This | # ]

@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).

[ Reply to This | # ]

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.

[ Reply to This | # ]

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.

[ Reply to This | # ]

(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

[ Reply to This | # ]

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...

[ Reply to This | # ]

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

[ Reply to This | # ]

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

[ Reply to This | # ]

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.

[ Reply to This | # ]

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!

[ Reply to This | # ]

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

[ Reply to This | # ]

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

[ Reply to This | # ]

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.

[ Reply to This | # ]

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.

[ Reply to This | # ]

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

[ Reply to This | # ]

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 :-)

[ Reply to This | # ]

Again,

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

[ Reply to This | # ]

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.

[ Reply to This | # ]

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...

[ Reply to This | # ]

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

[ Reply to This | # ]

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

[ Reply to This | # ]

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

[ Reply to This | # ]

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."

[ Reply to This | # ]