Re: Installing Leopard on my new Mini

Richard Tobin <richard@xxxxxxxxxxxxxxx> wrote:

In article <1i7djd7.u5pp3qo429srN%dempson@xxxxxxxxxxxxx>,
David Empson <dempson@xxxxxxxxxxxxx> wrote:

For a Mac with an Intel processor, to install Mac OS X (Tiger or
Leopard), the destination drive must be partitioned using the "GUID
Partition Table" scheme (GPT for short).

Is there any technical reason for this, or is it just Apple saying
"ha ha, you have to do it our way"?

I don't know of any technical reason, other than firmware updates only
working on GUID Partition Table (presumably due to limitations in the
firmware itself). GPT may offer other technical benefits over APM - I'm
not familiar enough with it.

Booting from Apple Partition Map probably requires some Apple supplied
extensions to Intel's standard EFI firmware, and by not officially
supporting booting from APM, Apple have the option of removing this
support in future firmware without having to do anything serious with
users' hard drives.

The current Leopard DVD is able to boot both PowerPC and Intel Macs, so
it is partitioned using APM. This means that all existing Intel Mac
models must support booting APM or they won't be able to boot Leopard.

With the official policy only allowing installing on GPT, there is
nothing stopping Apple from removing APM boot support in any model
released after the introduction of Leopard, as the original Leopard DVD
won't support installing on any of those models. Machine-specific DVDs
for the MacBook (Late 2007) and any later ones could be partitioned
using GPT, and their firmware could drop APM boot support.

This would only be a reasonable policy if they were planning to drop all
PowerPC support in the next major revision of Mac OS X, which would
allow them to release the next major OS upgrade on a GPT DVD. I think
that is premature.

It also seems unlikely at this stage because when they eventually update
the retail Leopard DVD (a new reference release), it will still need to
boot on all supported models, including PowerPC and more recently
introduced Intel Macs, which means it will have to be APM and those new
models must still support booting from an APM DVD.

A more likely scenario is that the next major upgrade of Mac OS X will
drop support for many more PowerPC models, and the remaining few could
get a firmware update which allowed booting them on GPT. This would
allow Apple to use a GPT DVD for 10.6 and drop APM boot support in
models introduced from late in the life cycle of 10.5.

--
David Empson
dempson@xxxxxxxxxxxxx
.

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