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Comment by feralchimp | Hacker News Reader

I really do not understand why any of the Mac Pros would lack the horsepower to run Mountain Lion. The GPU in mine is pretty weak, but it would be cheap to upgrade the GPU.

Here's hoping the installer either a) checks actual machine specs rather than machine "version number") (not likely), or b) can be cajoled (annoying).

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It's not a lack of horsepower. It's an infuriating artificial restriction against running 64-bit Darwin kernels on 32-bit EFI. There's no technical reason why a 64-bit kernel can't be launched by a 32-bit EFI, but for some reason Apple has decided that 64-bit kernels will only boot from 64-bit EFI, and Mountain Lion will ship with a 64-bit kernel.

See http://netkas.org/?p=830 for more.

edit: Oh, and as to your whitelist/blacklist point - yes, Mac OS X checks what systems it can be installed on by Board IDs stored in "InstallableMachines.plist," not by enumerating the hardware.

I can't remember where I heard this, so don't quote me, but I've heard it partially has to do with graphics kexts in some or all of those machines being 32-bit and a reluctance from Apple and the manufacturers (Intel, AMD, Nvidia) to update them. That said, I'm not sure how that would rule out the Mac Pro, then, because the chips I heard cited were the old Intel chips (950, x3100) and AMD chips (X1600).

Again, don't quote me!

edit: this assumes Apple is moving to 100% 64-bit.

This makes sense for non-Mac Pro machines, although so far it doesn't seem to be the case as Mountain Lion will actually run on those machines if they're added to SupportedHardware.plist [0].

However, in the case of the Mac Pro it's hard to see the restriction as anything other than arbitrary and frustrating.

0: http://osxdaily.com/2012/02/18/install-os-x-mountain-lion-de...

This is mildly depressing but highly informative. Thanks for the link.

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