Linked by moondevil on Wed 11th Jul 2012 22:49 UTC
Mac OS X Ars Technica is reporting that certain 64bit Mac models won't be able to run Mountain Lion. The problem is the graphic card drivers; these are still 32bit, and Apple is unwilling to update them to 64bit. A 64bit kernel can't load 32bit drivers, so that's that. Apple has a list of supported models on their Mountain Lion upgrade page, so you can easily check if your computer is capable of running Mountain Lion.
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64bit kernel in 32bit mode - i never got it
by lazar on Thu 12th Jul 2012 12:02 UTC
Member since:

This ist the link to a small tool, telling you in which mode your kernel booted.

I never quite understood how it works that I have a 64bit-EFI with a 64bit-kernel, that starts up in 32bit-mode and runs 32bit and 64bit applications alongside - as this app indicatates my 2011-MBP does with Snow Leopard.

You can use this tool also to force your kernel into 64bit mode on next boot - which I never tried.

I thought this strange mixture of 64bit/32bit-kernel mode was what allowed Snow Leopard to run 32bit drivers also.

First of all - how can a piece of kernel be 64bit and 32bit at the same time, if it's not just a 2-architecture binary file and bootmode decides which of the two ressources in this fork is loaded.

And if '32bit-mode' means that kernel operates in 32bit - how can it execude 64bit applications and kernelextensions?

I really don't get it.

And what happend in Mountain Lion, if Apple really has such an elaborate way of mixing 32bit and 64bit?

Reply Score: 1

lazar Member since:

Ok, I found the answer to my own question ;-)

Mac OS X loads the same kernel image and run it as a 32-bit process, although when run on 64-bit hardware, the 32-bit kernel switches into "long mode compatibility mode."

Still it sounds like magic - I thought in machine code you have to be very specific about 32 or 64bit.

Reply Parent Score: 1

toast88 Member since:

I really don't get it.

MacOS has actually a very unique design to run 32-bit and 64-bit applications. It's quite complicated.

If you have some time, watch this talk from CCC, it might shed some light onto it:


Reply Parent Score: 2