[Macbook] Lil' confused about 32/64 bit stuff w/C6

Aloha guys,
I have an Intel Macbook (see sig) Core 2 Duo running 10.6.7

This machine will not/cannot physically boot into 64bit.

The Apple Knowledge Base thingy says that even tho’ this is an ‘Intel Core 2 Duo’
'puter, this is normal behavior for this particular machine.

Yet some how this machine will run C6 in 64 bit with no problems.

How is this possible?

I always thought that 32 bit apps will/can run in a 64 bit environment

but that

64 bit apps will not/cannot run in a 32 bit environment.

So what’s goin’ on here?

Which brings up a more ‘macish’ question.
How can even the OS (10.6.7 64bit) even run on this machine?
But it does. And quite nicely too.

BTW I have no major probs with this machine using C6. (knock wood) (64 or 32bit)
I am just a lil confused/curious about all this.


I see no one has responded to your question. Im NOT SURE about this, but at least its a response!?
As far as I know, 64bit only takes advantage of MORE RAM and takes up a bit more space in installation files. So, I would THINK, 64bit apps WOULD run on 32bit OS. More or less efficient is beyond me! Im GUESSING LESS efficient due to the App/Plug-ins being bulkier? Wider car on a thinner street? :question:

Hi curteye,

Core 2 Duo processors ARE 64 bit processors therefore you can install and run 64 bit software. The first Intel Macbooks that came out in january of 2006 were Core Duos (without the “2”) and they were 32 bit processors, thus incapable to run 64 bit software. But your machine is a 64 bit system. What you mean by “This machine will not/cannot physically boot into 64bit” is probably that it doesn’t have a 64 bit EFI (Extensible Firmware Interface that boots the system) and therefore is not compatible with the 64 bit kernel of Snow Leopard. But in Mac OS X the capability to run 64 bit apps is independent from whether you boot the 32 or 64 bit kernel, the kernel will only load the hardware drivers and the most important system processes and leave the rest to the Darwin Unix layer and the different API’s on top of it. So even if your machine cannot boot the 64 bit kernel you can run 64 bit applications nevertheless on top of the 32 bit kernel. When operating with the 32 bit kernel the memory addressing is done via PAE (Physical Address Extension) that extends the available memory beyond the usual 32 bit limit of 4 GB, in the case of Mac OS X up to 32 GB of RAM. Only if you want to install more memory than that (the newer Mac Pro’s support up to 64 GB) you have to boot with the 64 bit kernel.

So, your installation of 10.6 is a 64 bit operating system on top of a 32 bit kernel.

Hope this helps!

Aloha and thanx guys for your posts.

@ parnasso
That explains it perfectly. I get it.

Thank you for the insight and your time.