Booting a GUID disk on PowerPC Macs

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
I Just made a very cool discovery while playing around in OpenFirmware on my G5 Quad that I think is worth sharing

which is that its OpenFirmware implementation can read disks with GUID partition schemes!

after discovering this I quickly cloned Leopard onto a GUID disk and I was able to boot from it :D (so much for people saying PowerPC macs can only boot from Apple partition Map! :p )

this is very good news especially for anyone who has a larger then 2.2TB drive that they wish to use in their PowerPC Mac as their startup disk (as APM only works properly with drives bellow 2.2TB)

however I suspect that this functionality is only available on the very last (Late?) 2005 PowerPC Macs, ill be testing more of my PPC systems for GUID boot-ability and updating this thread as I do :)
upload_2018-4-5_18-20-40.png
 

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
So how is this useful to us? It’s cool, but... ?
but what?... :confused:

Biggest thing this enables someone to do is allow them to use Drives bigger then 2.2TB as their boot drive (Apple partition Map does not work properly on volumes bigger then 2TiB/2.2TB), it also means if you have say Leopard on a broken intel Mac/on a HDD from an intel mac that you need to boot up for some reason and all you have is a 2005 PowerPC mac then you can do so :) )

Your next goal could be achieve that on Tiger. :D

It would be great if it works also for G4.
this is a Low Level Firmware thing the OS does not really come into play much here as long as it supports GUID/GPT it will be fine (which 10.4.11 does so I suspect tiger would boot up just fine, But I will test tiger at some point to be sure)

as for G4s I tested it on my Late 2004 iBook G4 which does not read GUID volumes so that machine is out, but My 15 inch PowerBook G4 DLSD happily read the GUID volume and booted from it, I still need to test my 17 inch DLSD for GUID/GPT compatibility (I also Have a Early 2005 PowerMac G5 7,3 that I will test GUID compatibility on, so I can figure out exactly when Apple added GUID support to PPC macs/OpenFirmware so far it seems to be 2005 PowerPC macs only, I want to figure out if early 2005 PowerPC macs support GUID/GPT or if just the very last Late 05 PPC macs like the DLSD/PCIe G5s support GPT/GUID)
 

Eriamjh1138@DAN

macrumors 6502a
Sep 16, 2007
620
417
BFE, MI
So if I have a partitioned drive, all of the volumes are formatted as GUID. Then I can boot intel and others can boot PPC.

That’s useful.
 

weckart

macrumors 603
Nov 7, 2004
5,032
2,320
so far it seems to be 2005 PowerPC macs only, I want to figure out if early 2005 PowerPC macs support GUID/GPT or if just the very last Late 05 PPC macs like the DLSD/PCIe G5s support GPT/GUID)
Indeed, it is only the latter PPC models that had that ability. This was discovered at the time but somehow stayed under the radar. I checked out this discussion when seeing if I could resize/create/delete an APM volume on the fly and found this (see reply sphns on April 10, 2006 - 8:46pm )

http://web.archive.org/web/20070509...om/tips/cli/nondestructively_resizing_volumes

I think there might also have been something on it on MacOSXhints but my memory is a bit fuzzy.

As for the resizing thing, two applications VolumeWorks and iPartition both do the job but nothing via diskutil, sadly.
 

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
Very cool :)

as for the Resizing thing Late versions of DU in Tiger (I know 10.4.11 can) and leopard+ can non destructively repartition/resize APM HFS volumes as long as they dont have Mac OS 9 Drivers installed :) (if you have Mac OS 9 drivers installed then it gets a bit tricker and I just use linux if i have to resize/partition a Volume with Mac OS 9 drivers installed)
 

weckart

macrumors 603
Nov 7, 2004
5,032
2,320
Very cool :)

as for the Resizing thing Late versions of DU in Tiger (I know 10.4.11 can) and leopard+ can non destructively repartition/resize APM HFS volumes as long as they dont have Mac OS 9 Drivers installed :) (if you have Mac OS 9 drivers installed then it gets a bit tricker and I just use linux if i have to resize/partition a Volume with Mac OS 9 drivers installed)
Yes, I knew this. Sadly, when I need to resize/move/delete there are always classic MacOS volumes involved. FWB Toolkit will resize volumes but only HFS volumes.
 
  • Like
Reactions: LightBulbFun

vddrnnr

macrumors 6502
Jan 23, 2017
430
573
Hi all,

Using GUID also has another benefit you can create different partition types
not only HFS because APM does not support the others, and modern OSs support GUID
for sure.
This way you can create EXT3/4 and FAT32 volumes without limitations which helps to store data
in other partition types and make them accessible on OSs which do not support HFS.
This will also help dual booting... I think.

Best regards,
voidRunner
 

DearthnVader

macrumors 65816
Dec 17, 2015
1,150
5,737
Red Springs, NC
The question is, is Open Firmware on these systems that support GUID able to read the FAT32 partition?

If so, we could copy a Grub/Grub2 ELF binary to boot our systems;-)

I know from MophOS that Open Firmware on Power Mac's can boot from a FAT32 USB stick, but it may or may not be a limitation of OF that the FAT32 partition be the ONLY partition on the disk?????????
 

Jubadub

macrumors regular
Nov 1, 2017
198
232
This made me wonder, but are PCIe-connected drives detected in OF? If they are, do they have to be ADB, GPT or either one works?
 

weckart

macrumors 603
Nov 7, 2004
5,032
2,320
This made me wonder, but are PCIe-connected drives detected in OF? If they are, do they have to be ADB, GPT or either one works?
Depends what the protocol is. For PPC machines, I have only ever seen SATA adapter cards used.
 

LightBulbFun

macrumors 68020
Original poster
Nov 17, 2013
2,298
2,233
London UK
sadly I dont think Open Firmware on these macs contains any sort of AHCI driver

so a SATA card would probably not be bootable

if you could write an open firmware AHCI driver then you could boot from one
 
  • Like
Reactions: Jubadub

DearthnVader

macrumors 65816
Dec 17, 2015
1,150
5,737
Red Springs, NC
A little more info, as @LightBulbFun said, and I also tested, the Late 2004 iBook G4's can't read GUID disks at the firmware level.

However, the Mid 2005 iBook G4's can.

.....And you can boot from the Fat32 partition of a GUID disk, even loading BootX works, I'll have to check if the Mac OS ROM can be loaded from a FAT32 partition.

I seem to recall something about non-hfs/hfs+ not preserving the Resource Fork????
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.