A APM and GPT riddle

[sjs]

hi

My macbook's internal HD is partitioned as Apple Partition Map, yett boots up fine!

Two weeks ago i reinstalled from original DVD as per your suggestion and then used Migration Assistant ("from other computer attached to this Mac") to migrate user data from an attached GPT FW disk. All worked fine.

Today I need to repeat the process but can no longer install to the internal drive because its now APM. I presume the drive must have been GPT as of 2 weeks ago since it installed fine then. In fact, I think I had a similar problem then, and I had to reformat the drive GPT back then too.


1) Isnt this supposed to be impossbile to boot intel macbook from APM yet I am doing it?
2) How can it spontaneously change?

A real riddle!

ps - i am going to hold off repartitioning as GPT/restoring until i hear back from you in case you want to verify something on this disk

[dnanian]

You really, really want to make sure your internal drive is partitioned as GUID, even if it works. You'll be sorry if not... it's not that it's impossible, it's that it's unsupported, and it's likely install DVDs won't work with it.

[sjs]

Thanks for the amazingly fast resonse as usual.

But what about The Riddle? Part 2 of my question? That is, how did it change from GPT->APM and how do I keep it from doing that again?

The proof that this disk was indeed GPT as of 2 weeks ago is that 2 weeks ago, I was able to use the System Restore DVDs and today I am not.

Last time I had to reformat the internal APM drive to GPT as well. So this is now the *second* the disk has been repartitioned as GPT (assuming they came GPT from the factory), and if I do it again today, it will be the third time!

Is there any known way of even of even doing that? diskutil does not even have the option of replacing a live partition map.


Tell me please, am I going crazy?
:-)

In the meanwhile, will reformat it again as GPT...

[dnanian]

It can't do that, as far as I know. It's quite low-level, and I've certainly never seem one mysteriously convert formats... never heard of it, either!

[sjs]

well, you've officially heard of it now :-)

just for kicks look at my last post here and tell me how i managed to do this:

http://www.shirt-pocket.com/forums/showthread.php?t=2142

at least i have these threads to document my descent into madness...

[dnanian]

Yah. Don't get it.

[sjs]

grasping at straws here but can only think of one causal factor, highly improbably as it is.

my macbook has some kind of PMU bug i think... If the macbook is running from battery and you plug in a FW drive (powered) the machine instantly turns off. if it sleeps and gets unplugged from mains power while a FW drive is plugged in, it won't wake up. Reseting the PMU as described by apple solves, temporarily #1 until #2 takes place.

i think they will have to replace my mobo..

how this magically transforms a partition seems unrelated and impossible to me, i know...

i only bring it up because this mac is already acting funny...

[dnanian]

Yeah. But even if it's acting super-ultra-mega-funny, it wouldn't mysteriously convert partition formats. Doing so would destroy your data!

[sjs]

exactly!

so since i Restored from DVD fine just a few weeks ago...and we both know you can't restore the DVD if it was an APM disk...

my only conclusion is someone has been substituting my memories ala Eternal Sunshine.

[dnanian]

Could be! Seriously, though, I really don't know how this could possibly happen. I know I've said it before, but it needs to be said again.