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Discussion in 'MacBook Pro' started by irajoshbernstie, Oct 21, 2010.
Are the Macbook Pros 64bit and what does that mean 64 bit?
yes they are 64 bit but the os doesn't enable it by default you have to turn it on by holding down the "6" and the "4" key on your keyboard during boot up each time.
Depends on the model but generally all the recent ones (08-10 models) have 64bit EFI plus the required drivers which allow you boot the 64bit kernel of Snow Leopard by doing the '6' and '4' salute)
64bit allows you address more RAM and use it more efficiently...and of course run 64bit GUI applications. The End.
Just FYI, a 32bit Kernel does not mean that the rest of the system is not capable of utilising 64bit processors and applications. OS X has been 64bit ready for ages.
The 64bit Kernel becomes handy if you want to use more than 32GB of RAM. Some people argue that they've seen a HUGE difference between 32 and 64bit Kernel, but personally, I haven't seen any difference whatsoever on my 2009 Mac Pro, testing various applications.
If we can believe some users, the latest version of Logic actually benefits a little from a 64bit kernel. Not by much though. It's no silver bullet for a slow machine.
32 bit, or x86, processor architectures can only access up to about 4GB of physical memory. The actual number is usually lower (3.2-3.8) due to OS restrictions.
64 bit, or x64, processor architectures can access an amount of physical memory that, at this moment in time, is way more RAM than you will ever need (a few PBs).
By default, MBPs boot into the 32 bit kernel (the kernel can only access 4 gigs of memory), but Snow Leopard has a 64 bit kernel that can be booted by holding down the 6 and 4 keys during bootup (or by modifying a system Plist file). The 64 bit kernel wont show any improvements at this moment in time.
I apologize if I am wrong here, but I believe the kernel needs to allocate a certain small amount of memory for itself for every GB of RAM you have installed. If you have 94 gigs of RAM (which wont be too huge of an amount in the near future), the kernel needs like 3 gigs of that for itself. If you are running a 32 bit kernel, then it is limited to accessing 4GB of those 94 gigs. In theory, if you are running a 64 bit kernel, then it can allocate all the memory it needs.
In Snow Leopard, 64 bit apps will be able to allocate more than 4 gigs even when you are running a 32 bit kernel, so don't worry about that. I get bored and just jump from one Wikipedia article to another. I search for something interesting and read that article, opening any interesting links from that page in another tab. When I finish with the first article I will move on to the next. Repeat…
This is all off the top of my head and isn't specifically accurate, but it is all true.
The 4GB memory limit applies for a true 32bit system, that's true.
The Intel architecture the Mac uses, however, uses a nifty little thing called PAE (physical address extensions), which allow the system to address 36-bit addresses. This is the reason that even 32bit kernel Macs can address more than 4GB of RAM. Actually the limit would the 64GB, Apple limits it to 32GB though, which makes the 64bit kernel mandatory for memory sizes of 32GB+ (only available for Mac Pros atm).
Can you validate the "facts" in the rest of my post?
I cant find the specific article or blog post where I read most of that information.
OS X has been 64-bit capable for ages.
all MBPs since 2007 (Santa Rosa) can boot into a 64-bit kernel, but they are all defaulted to the 32-bit kernel. however, there is no drawback to using the 32-bit kernel. it can use much more than 4GB.
32-bit Windows, though, can't use more than 3.2GB.
I don't have that problem on the MacPro with SL. It stays in 64bit mode all the time. Will only change when I tell it too.
Recent MPs have 64bit enabled by default.
anyone have instructions on how to change the plist file to boot MBP in 64bit mode all the time? I hate to press '6' and '4' everytime i boot the machine.
Go here: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
Open it up and, if it isn't there already, add a String called Kernel Flags. set the value to arch=x86_64
What app did you opent that plist with? its opening in TextEdit as xml file for me
Oh, sorry. Developer plist editor. Should look like this then.
looks like my new MBP already boots in 64bit without any modifications...too bad, i just saw this.
64 bit apps can run when not in 64 bit mode. 64 bit mode just means the kernel is 64 bit.
I just tried to modify the plist file and got access error..looking at Get Info, it says only "system" has Read&Write access on this file. How do I login as "system"?
Click The Lock (Bottom Right) And Authenticate
If You See Your Name, Go To Next Step
If You Don't See Your Name, Click [+] And Choose Your Name
Set Your Permissions To "Read & Write"
If you still get the error just save the plist to another location (Shift+Command+S) and then drop it into the SystemConfiguration folder. You may have to authenticate, please do so.
You are the BEST ...
Before you sent me these instructions, I enabled root user on my laptop and logged in as root and modified the file...now my kernel shows as 64bit ... Thanks for all your help, appreciate it.
You could have just typed: sudo nvram boot-args=arch=x86_64″ in Terminal and been done. LOL
As mentioned before, some Mac Pros and xServes have 64 bit enabled by default. Most certianly the recent ones.
Why doesn't apple ship with the 64-bit kernel as default?
Is there any benefit if the MBP can only have 8GB of physical RAM anyway?