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.
Thread beginning with comment 526526
To read all comments associated with this story, please click here.
64bit kernel in 32bit mode - i never got it
by lazar on Thu 12th Jul 2012 12:02 UTC
lazar
Member since:
2008-12-10

http://ahatfullofsky.comuv.com/English/Programs/SMS/SMS.html

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:
2008-12-10

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

http://www.appleinsider.com/articles/08/10/28/road_to_mac_os_x_snow...


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:
2009-09-23

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:

http://www.youtube.com/watch?v=-7GMHB3Plc8

Adrian

Reply Parent Score: 2