Please verify my asssumptions about PPC and Intel Mac partition sturcture

Jim Harris jimrh at
Wed Feb 8 04:00:20 EST 2012

Please examine my understanding of the PPC and Intel Mac partitioning structure, and either confirm that my understanding is correct, or let me know what it really is.



1.  I am assuming that this structure is true for *ANY* PPC based Mac:  G3, G4, G5, G6, G117, or whatever (laughing!)
2.  BCD creates TWO partitions for each one created using "Disk Utility" on the Mac
   a.  A "hidden" metadata partition
   b.  The actual partition created.

In other words, if I create five partitions, labeled "A", "B", "C", "D", and "E" within Disk Utility, what I actually get (when using Linux to view the structure is this:
(a) "A", (b) "B", (c) "C", (d) "D", and (e) "E" - where partitions (a) through (e) are metadata partitions associated with partitions  "A" through "E"

What this also means, is that if I create five partitions - numbered 1 through 5 - within the actual partition structure itself, they would be numbered 2 through 10, being the even numbered partitions.  That is, five partitions created in Disk Utility, (1 through 5) become partitions 2, 4, 6, 8, and 10.

I have noticed that this is true on my G3 PPC.  I would like to know if this is generally true on *ALL* PPC based Mac's



1.  Is the partition structure on an Intel Mac the same as the structure on a PPC Mac?  (i.e.  BCD creates two partitions for each one created in Disk Utility and they are structured in the same way.)

2.  I know that on the PPC, the first partition created - which will become the bootstrap partition - is formatted as HFS+
     I also know that on the Intel Mac, the bootstrap partition is not formatted because Yaboot writes to the "raw" partition itself.

Question:  When you are creating a multi-boot environment on an Intel Mac, do you create the same kind of structure, except that you do NOT format the bootstrap partition?

IOW, when you lay out the partition structure in Disk Utility, is the first partition "unformatted" (or marked as "unused"?)


Thanks for any help you can provide!

p.s.  Don’t forget – I’m always here for all of your computer or networking needs.

Jim "JR" Harris 
Principal Engineer / Owner
Arrowhead Computer Consulting, LLC
Authorized Avira Security Solutions Reseller
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