Snow Leopard 32bit vs 64bit - FAQ

[swegen]

I put together boot.efi x64 patches for all models that do not support native booting into 64-bit kernel.

Just run patch, enter admin password (required to modify a system file), reboot and you should boot into 64-bit kernel.
Restore to original boot.efi also included.

x64patch-10.6.8.tar.bz2
x64patch-10.7.tar.bz2

I have tested the patches with MacBook3,1 & MacBookAir3,2

[Dr. McKay]

Originally Posted by Winni

Also, the memory limitation of desktop Windows is in part driver- and chipset related and not a limitation of the OS itself. Especially on a Mac it is rather "interesting" to observe that 32-Bit Windows can only use a maximum of 2 GB RAM while other operating systems can use the full amount. Apple has done a poor job with their Windows drivers, it seems.

I want to install Windows 7 on a bootcamp partition on my iMac (Early 2008 2.8Ghz Core2Duo, 4Gb of RAM, ATI Radeon HD2600 Pro, OS X.6.8). I've been in doubt as to which version to install.
Although my iMac is not officially supported according to Apple, I CAN install 64-bit Windows 7 (just need to install the x64 bootcamp drivers using the command line, ie DOS) ; nonetheless, it would be less of a hassle if I just installed the 32-bit version.
I would use Win7 to learn a bit more about the OS, and I'd be running light apps like different web browsers, open office, stuff like that. Also, I would like to use Win7 for games, especially Wow and Valve games via Steam, because games just run better on Windows.

Now, as far as I know, a 32-bit version of Win7 would allow me to use around 3.3Gb of RAM, the remaining 700Mb being reserved (also read something about the amount of video RAM playing a part in that).
In any case, I believe that 3.3 GB of RAM would be more than enough for what I want to do, and I don't think that 64-bit Win7 would be that much faster/snappier, seeing that I only have 4Gb of RAM.

However, now you're saying that 32-bit Windows on the Mac can address no more than 2Gb ? If that's true, then I'd be more inclined to install x64 Win7. Unless you're mistaken.

Bottom line, what advantages would x64 Win7 give me over x86 Win7, taking into account the 'low level' stuff I want to do with my bootcamp partition ? Unless the '2Gb statement is true, in which case I'm going for the x64-version.

[jaimedormer]

Hi,

I was renaming a folder without the quotes from "MEDIUMFORMAT" to ".MEDIUMFORMAT" and accidentally hit the enter key oops... *&^$#@@, it is now nowhere to be found, I have looked in the trash, searched for it etc, no good, does anyone know how I can recover it ? Jaime

[IvanOhio]

1. I don't understand 64 bit.

A. You don't HAVE to know about 64 bit. For most users of OS X, it won't matter.

The Application delivery mechanism for future OSX Snow Leopard apps will still be Universal Binary, which will include BOTH 32bit and 64bit code if available.

The default SL kernel is 32 bit which is more compatible. Note that the Snow Leopard 32 bit kernel can still run 64 bit processes that allows access to more memory, useful for some power users.

The only reason you have to know about 32bit or 64bit is if you are running windows.

With Windows there is a 4GB total memory limit with 32 bit windows. Mac OS is different. Even Macs running Leopard can contain and use far more RAM than the 4 GB limit the "32-bit" qualifier might seem to imply.

Yes, 64-bit kernel (K64) allows use of a very large number of RAM, 16 exabytes to be exactly, but do you have any apps that need more than a few GB of RAM?

With Windows you need to download a different version of the app / program / driver for different version of windows os. On Mac OS, you download 1 Universal Binary which will work on all 32bit and 64bit (if available) installs for that Mac OS.

Yes you are suppose to get higher benchmarks on certain artificial test for running K64, but in daily use you won't notice a difference for almost most users do on Mac OS X.

I need to correct a few things posted here.

There is huge misunderstanding by people concerning the difference between 32 bit and 64 bit operating systems. I am seeing it in many forums lately. And there is some confusion about physical and virtual memory.

The original poster has some information right but also wrong.

First, let me address the 32 bit information. Some of information is correct however they forgot a key phrase, Virtual Address Space. The 4 Gb referred to is located in virtual not physical memory. In a 32 bit OS, processes are given 4 GB of Virtual Address Space to operate. However, the process my only use 2 GB and rest is system related. That is why you are seeing the trend to go to 64 bit in operating systems.

Second, now the beauty of 64 bit operating system. Why it is so much better is the Virtual Address Space. According to the information I found about OS X, it uses 18 exabytes of Virtual Address Space. I believe that translates to about 10 terabytes +/- of Virtual Address Space. So, this allows each individual process more that enough room to work and play. That is the keep to understand 64 bit OS. You have a larger address space to work with.

Third, physical vs virtual memory. There is huge difference between physical and virtual memory. Physical is what you see and touch. Virtual is there but you can not see it but it is there.

You can install 8 GB of physical RAM into your system. However, your OS most likely use about 1 to 2 GB under normal load. And rest is truly free and can be used when needed. If your system used all of physical memory then your computer would not work.

Now the virtual memory is always larger than physical. That is Virtual Address Space allowing it to work and play better with others.

I just wanted to try to clarify this because there is so much confusion going on. I see to many incorrect advice and information given out.

[Philipppa]

Originally Posted by Washac

Hi

How do I see if I am booting into 32 or 64 ?

If I want to change this, how do I do it please ?


Thanks....

It's easy, you could read some guides from macworld, i have resolved the problem.

[brdeveloper]

Correct me if I'm wrong about using 32-bit kernel/apps:

1) 32-bit kernel fetches data using PAE so it needs a further query to memory tables (an extra memory access which could theoretically increase memory fetch time in something like 33%).

However, I imagine that if processes are limited to 4GB addressing, an app currently executing in a 32-bit kernal can perform just as non-PAE apps since the Kernel can skip at least one query to page tables. So performance decrease is only perceived in kernel memory management or when executing 64-bit apps in a 32-bit kernel.

2) 32-bit apps usually tend to limit their literal datatypes in 32-bit size while 64-bit apps will tend to default to 64-bits, e.g. the default size the integer datatype occupies in memory. So 64-bit apps can waste a little more memory space. PHP and and other non-typed/interpreted languages would suffer more on this issue since the language have to default to the larger data size to prevent future overflows during execution. Typed, compiled languages suffer less and it's up to the programmer saving or wasting memory.

Am I correct?
----------
In short:
32-bit kernel - slightly slower than 64-bit kernel
32-bit apps - usually saves a little more memory than 64-bit apps

[billye1952]

I have a 2011 july macbook air. (lion 10.2) I am having a field day in trying convert my lion to snow leopard. I used the disk utility to eases the ssd drive.
So, the lion recovery system will not auto it back system..Still did not work.
Can somebody help me.

[Intell]

Originally Posted by billye1952

I have a 2011 july macbook air. (lion 10.2) I am having a field day in trying convert my lion to snow leopard. I used the disk utility to eases the ssd drive.
So, the lion recovery system will not auto it back system..Still did not work.
Can somebody help me.

They cannot run Snow Leopard without massive usability problems. Even if you get it on there, it'll kernel panic or freeze at the login screen.

[Modernape]

Originally Posted by brdeveloper

Correct me if I'm wrong about using 32-bit kernel/apps:

Am I correct?
----------
In short:
32-bit kernel - slightly slower than 64-bit kernel
32-bit apps - usually saves a little more memory than 64-bit apps

You are very correct - some benchmarks from an MIT blog. Where they summarise -

biggest difference was in memory allocation, where the difference was almost a factor of two.The next biggest difference was in the thread benchmarks, where the 64-bit kernel had a roughly 30% improvement in time. Finally, the 64-bit kernel had over a 10% improvement in large block disk transfer speed

[steventay]

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[netventurer]

Would you be able to assist me in getting a version that will work in OSX 10.8 (Mountain Lion)?