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64-bit and Snow Leopard – What 64-bit means for you

vansmith

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To quickly answer my title post, probably nothing. This doesn’t mean though that it can’t hurt to understand what it means for you. For the sake of brevity, I will not be discussing the differences between 32-bit and 64-bit simply because that is irrelevant to the purpose of this post. The purpose here is to explain the "usefulness" of 64-bit to the daily usage of your Mac. In case you’re interested, I quote Apple’s description of what increased 64-bit support means: "Today’s Mac computers can hold up to 32GB of physical memory, but the 32-bit applications that run on them can address only 4GB of RAM at a time. 64-bit computing shatters that barrier by enabling applications to address a theoretical 16 billion gigabytes of memory, or 16 exabytes. It can also enable computers to crunch twice the data per clock cycle, which can dramatically speed up numeric calculations and other tasks."

First off, this is not the first release of OS X to include 64-bit support. What is important to note is that the pervasiveness of 64-bit support is now at a point where it affects the core of the machine should you choose to utilize it. Secondly, just because there is increased 64-bit support doesn’t mean that you should or need to utilize it. Many of us will work with 32-bit software most of the time or, even if you do use 64-bit software (which encompasses most of the system software now), you probably won’t be using features that are unique to 64-bit. Nonetheless, here are some questions that I have seen popping up and my best attempts to answer them.

Q: Does my Mac support 64-bit?
A: I’m only going to answer this in regard to those who use Intel Macs simply because of the dropped support of PPC Macs in Snow Leopard. For those who use Intel Macs, the quickest way to determine if you are using a 64-bit Mac is to see what Intel processor you are using. Simply put, if you are using an Intel Core Duo, you are using a 32-bit processor. If you are using an Intel Core 2 Duo on the other hand, you are using a 64-bit processor. To check the type of processor you are using, simply go to  > About This Mac > Processor. On my machine for example, I am using a "2.1 GHz Intel Core 2 Duo" and therefore, I have a 64-bit capable processor.

Q: If I don’t have a 64-bit capable processor, can I still use Snow Leopard?
A: Yes but you won’t get any of the arguable benefits that come with 64-bit computing. This does not render Snow Leopard useless as many of the great enhancements and improvements are independent of the increased 64-bit support such as Grand Central Dispatch and OpenCL. For descriptions of these technologies, go here. In fact, for the near future at least, those who boot into a 64-bit kernel will likely experience more problems than those who stick with the default 32-bit kernel.

Q: I have heard that I can boot into a 64-bit kernel. Should I?
A: While for some the idea of booting into a 64-bit kernel is nice, it isn’t advisable (for now). The reason this is the case is because of particular software that depends on 32-bit kernel extensions. I won’t go into great detail here as to what kernel extensions are but 32-bit kernel extensions depend on a 32-bit kernel and 64-bit kernel extensions depend on a 64-bit kernel. While this may seem irrelevant to the average user, using the proper kernel is imperative to the proper operation of particular pieces of software.

As an example, here is the status of the three major virtualization options and their 64-bit kernel support. As you can see here, Parallels is not supported on a “Snow Leopard 64bit Host”. The VMWare "Team Fusion" has also stated that, "While VMware Fusion 2.0.5 offers experimental support for the 32-bit version of Snow Leopard, VMware Fusion 2.0.5 is NOT compatible with the 64-bit version of Snow Leopard." I'm still unsure as to the status of VirtualBox under a 64-bit kernel (I have read conflicting things) but I will get back to you once I try. The important thing to get from this is that you shouuld check the status of software you use frequently before you boot into a 64-bit kernel. This should not be much of an issue though for most people as Snow Leopard defaults to a 32-bit kernel.

Q: I understand the problems that may come with booting into a 64-bit kernel but I still want to try it. How do I do this?
A: Should you wish to boot into a 64-bit kernel, you can hold down the 6 and 4 buttons during boot. It is strongly advised that you test all critical applications first before you start using them for important projects, work, etc. If in doubt, don't boot into a 64-bit kernel until you hear from the software maker that either the application is known to work with a 64-bit kernel or a software update is made available.

Q: How do I check if I am running a 64-bit kernel?
A: Instead of explaining it myself, I simply refer to the VMWare blog post mentioned earlier (see here) which has clear instructions on how to check whether or not you are running a 64-bit kernel.

If you have any questions that aren’t answered here, don’t hesitate to ask and we will do our best to answer them.

EDIT: Forgot links first time around.
 
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Nice thread, I have Intel core 2 do its all good but is 2GB enough RAM to use 64-bit?
 
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In which case, if booting in to 64 bit kernel would not support some of the third party applications, what is the point in Snow Leopard!
 
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its still confusing for me... i have a 2.0 ghz macbook intel core 2 duo, 4gb ram

does snow leopard really change anything? cuz i just installed it and i havent noticed any differences

except safari opened really fast
 

vansmith

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In which case, if booting in to 64 bit kernel would not support some of the third party applications, what is the point in Snow Leopard!
The transition has to occur eventually. Either the operating system or application pool has to move to 64-bit at some point.

does snow leopard really change anything? cuz i just installed it and i havent noticed any differences
As I mention in question 2, there is more to SL than more pervasive 64-bit support.
 
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Just to chime in, remember that a 64-bit processor with a 32-bit EFI will only run in 32-bit mode.

My Mid-2007 MacBook won't boot into 64-bit mode because of it's 32-bit EFI, the same reason I can only address 3 gigs of RAM.
 
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In which case, if booting in to 64 bit kernel would not support some of the third party applications, what is the point in Snow Leopard!
The 32bit kernel will still run 64bit applications natively.
 

vansmith

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Just to chime in, remember that a 64-bit processor with a 32-bit EFI will only run in 32-bit mode.

My Mid-2007 MacBook won't boot into 64-bit mode because of it's 32-bit EFI, the same reason I can only address 3 gigs of RAM.
Very true and good point. As stated in this OSNews article, the fact that you have a 32-bit EFI does limit you to booting into a 32-bit kernel despite the fact that this is an artificial limitation. If you want to check whether you have a 32-bit or 64-bit EFI, execute the following command (again, thanks to that OSNews article) in the Terminal (/Applications/Utilities):
Code:
ioreg -l -p IODeviceTree | grep firmware-abi
On my early 2008 MB, that command returns the following: | | "firmware-abi" = <"EFI64">. From this, I can see that I have a 64-bit EFI as denoted by the EFI64 at the end of that result. If you see EFI32, you have a 32-bit EFI. That said, that article states that on MacBooks, it is irrelevant if you have a 32-bit or 64-bit EFI - you will only be able to boot into a 32-bit kernel (again, artificial limitation imposed by Apple). I don't have SL yet - anyone tested this?
 

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Q: Does my Mac support 64-bit?
A: I’m only going to answer this in regard to those who use Intel Macs simply because of the dropped support of PPC Macs in Snow Leopard. For those who use Intel Macs, the quickest way to determine if you are using a 64-bit Mac is to see what Intel processor you are using. Simply put, if you are using an Intel Core Duo, you are using a 32-bit processor. If you are using an Intel Core 2 Duo on the other hand, you are using a 64-bit processor. To check the type of processor you are using, simply go to  > About This Mac > Processor. On my machine for example, I am using a "2.1 GHz Intel Core 2 Duo" and therefore, I have a 64-bit capable processor.
I scanned this thread & didn't see it mentioned...so for completeness I wanted to mention that some folks when they do the "64-bit processor check" procedure listed above...in addition to getting:

- Intel Core Duo
- Intel Core 2 Duo

You may also get (if you have a Mac Pro):

- Intel Xeon (with some multiple of cores, dual, quad)

The Xeon processor is also 64-bit.

- Nick

p.s. I apologize if this detail was already mentioned in this thread, and I missed it.
 
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Just to chime in, remember that a 64-bit processor with a 32-bit EFI will only run in 32-bit mode.

My Mid-2007 MacBook won't boot into 64-bit mode because of it's 32-bit EFI, the same reason I can only address 3 gigs of RAM.
I thought that any intel core 2 duo processor would boot into 64-bit mode. I am also using the mid-07 macbook and i just checked the terminal and it has the 32-bit EFI so thats a bummer.
 
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Has anyone booted and tried out 64-bit mode?
System Software Overview:

System Version: Mac OS X 10.6 (10A432)
Kernel Version: Darwin 10.0.0
Boot Volume: Macintosh HD
Boot Mode: Normal
Computer Name: MDNMBP
User Name: Marc De Neef (marcdeneef)
Secure Virtual Memory: Enabled
64-bit Kernel and Extensions: Yes
Time since boot: 15:06



Yep, Doesn't make one bit of difference in my situation.
Everything runs smoothly boot in 32 and 64 and the machine is much more responsive either way.

Cheers ... McBie
 

vansmith

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Yep, Doesn't make one bit of difference in my situation.
Everything runs smoothly boot in 32 and 64 and the machine is much more responsive either way.
You're right, it probably won't make a difference until you try to use applications that depend on 32-bit kernel extensions such as the virtualization solutions. The 32-bit kernel doesn't preclude the successful use of 64-bit applications as well so there is little to gain from going "even more 64-bit" (right now at least).
 
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The 32bit kernel will still run 64bit applications natively.

You are exactly right!. I agree with you 100%

But, won't capable of using the 64 bit advantages obviously.....Isn't it?

I am disappointed with such a void blown into a so called the world's most advanced operating system by Apple.
 

vansmith

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Not defaulting to a 64-bit kernel was a smart move by Apple as most of the kernel extensions made available either by Apple or through applications are compiled for a 32-bit kernel. Moving to a 64-bit kernel precludes the use of applications that depend on 32-bit kexts as you can't load 32-bit kexts in a 64-bit kernel.
 
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ok I got a simple question to add to the discussion ... if I boot into 64-bit kernel by pressing the 6 and 4 keys, does that make the option default? if so, how do I change back to 32-bit? by pressing 3 and 2?

I would try it out, but I won't get back to my mac until tonight :D

tnx for a reply
 
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Pressing 6 and 4 to boot in 64 bit does not make that choice permanent

If you reboot again, the system will reboot in 32 bit by default.

Cheers ... McBie
 
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