Does Boot Camp Assistant Partition It in GUID or MBR?

Hi,

first of: have a thorough read of the BootCamp Installation Guide to be found inside the BootCamp Assistant or here http://www.apple.com/support/bootcamp/

1 - the BootCamp Assistant (BCA) "only adds" a partition but does not alter the partition scheme used. So it remains a GPT but uses a sort of 'hybrid GPT/MBR partition table'.

2 - the BCA only preformats the new partition with FAT32, but you need to reformat it to either FAT32 or NTFS during the WIndows installation Pages 6 and following of the Installation Gudie).

3 - that's where the 'hybrid GPT/MBR partition table' comes into play.

Regards

Stefan

Hi,

have a read here http://refit.sourceforge.net/myths/

While GPT in general is supported with Windows 7, the implementation itself lacks some "refinery"... 😉

Happy computing

Stefan

Microsoft recommends GPT for 2TB and larger volumes.
MBR can't boot from a volume larger than 1.9TB.
Windows 7 can see GPT just find, but not HFS+, and AppleHFS and MNT are buggy.
Disk Utility can create a drive that uses MBR.
GPT has support for sub-tables and for Master Boot Record.
Apple's implementation of MBR might be on the weak side.
Windows 7 wants to actually have and boot from the 100MB system partition.
Apple, Intel, Microsoft, Sun etc are members of EFI Group and Unified EFI is supported on Windows Vista SP1 64-bit and later 64-bit versions, but Apple's is more proprietary and differs, but is the sole reason really for Apple's excluding and including which Macs are "supported" (which really isn't true) running Windows 64-bit (Vista/7) - that they have to have EFI64 or UEFI 2.x.

The external drive is likely something else, as you could format a drive to GPT and NTFS and have it work fine.

The best way to 'clean' a drive of all partition tables and volumes is with Windows and something like WD Lifeguard or similar tool.

As for hybrid, while some Macs can now boot by default to 64-bit kernel mode, I prefer the "from the ground up" of Windows 7 64-bit which still supports and runs 32-bit apps, but of course mandates 64-bit drivers in places.

Your Apple disks not only have GPT, but have to have other partitions like EFI (128MB) after any HFS partition. GPT does have an MBR - see the Apple tech note #2166.

Windows and GPT FAQ
http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx

*Secrets of GPT* http://developer.apple.com/library/mac/#technotes/tn2006/tn2166.html

Table 1: GPT Summary

Block Description
0 Protective MBR
1 Partition Table Header (primary)
2 through 2+b-1 Partition Entry Array (primary)
2+b through n-2-b partition data
n-2-b+1 through n-2 Partition Entry Array (backup)
n-1 Partition Table Header (backup)

The protective MBR is an MBR that defines a single partition entry that covers the entire area of the disk used by GPT structures and partitions. It is designed to prevent GPT-unaware programs from accidentally modifying a GPT disk. A GPT-unaware program sees the GPT disk as an MBR disk with a single, unknown partition. In a way, this is like the HFS wrapper around an HFS Plus disk.

Alvin777 wrote:
Thanks. The GPT detection or implementation on Windows then is not perfect but possible? How can I make Windows 7 64-bit see my GUID USB external drive then [OS X see this external drive as bootable but on Windows 7 under the Boot Camp control panel it doesn't (although it doesn't really boot Boot Camp from the external drive but switches to Boot Camp on the internal drive). What could be the explanation for this?)

The short answer: Microsoft doen't want Windows to be bootable/instalable on external harddisks.

The longer answer: You can find instructions to install and boot Windows of an external harddisk on the internet.
But all these instructions only work with USB-connected harddisks and require quite some doing.

Is there any adjustment that could be made to the registry of Windows 7 to make it detect GUID external drives? I hope the industry would standardize things even more with file formats and boot sector format (is this what GUID, MBR is called by the way?).

I am not aware of registry-hacks for Windows 7 for this.
MBR and GPT (GUID partition table) are partitioning schemes http://en.wikipedia.org/wiki/GUIDPartitionTable and describe the layout of the partition table on a harddisk.

The main problem with the transition from MBR to GPT is that until recently there was no need for the manufacturer to do it.
Now there are 3TB harddisks avaiable which exceed the capabilities of MBR so we might/will see some improvements in the future.

Stefan

You are confusing partition maps with user volumes.

Windows has fine GPT but it designed to be used with NTFS. Also supports Extensibe Firmware System partitions. So no lack there.

If you say clearly, and I don't think you have, that you have somehow put Windows OS on external USB (pulled from another system)? THAT seems to be the original question but you posts haven't been clear and just dance around the heart of the thread.

A PC can use eSATA but it also gives access to the BIOS to select the boot drive.

And as the article above: in order to boot from GPT you need to have EFI64.

Windows is fooled and does see the protective MBR in order to prevent clobbering a drive.