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Bootable partitions must start before 1024 cyl


fprince
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Greetings y'all!

 

This is my first post, so... Let me say hi :-) and thanks for creating and developing a solid knowledge base.

 

Now to the point. This may be obvious but again I haven't seen that being clearly stated.

 

A partition MUST start before the 1024 cylinder in order to be bootable. This information is probably especialy useful for those who are making a dual (multiple) boot system. So, no matter how many and which operating systems you are going to install and whatever boot loader you plan to use, make sure the partition for the boot loader starts below the 1024 cyl boundary.

 

Please note that when you chose to use OS X' native boot loader and you did not abide to the 1024 cyl rule, your system 

ill boot only from the installation DVD but not the hard drive. 

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Greetings y'all!

 

This is my first post, so... Let me say hi :-) and thanks for creating and developing a solid knowledge base.

 

Now to the point. This may be obvious but again I haven't seen that being clearly stated.

 

A partition MUST start before the 1024 cylinder in order to be bootable. This information is probably especialy useful for those who are making a dual (multiple) boot system. So, no matter how many and which operating systems you are going to install and whatever boot loader you plan to use, make sure the partition for the boot loader starts below the 1024 cyl boundary.

 

Please note that when you chose to use OS X' native boot loader and you did not abide to the 1024 cyl rule, your system will boot only from the installation DVD but not the hard drive.

 

You can use grub to boot past 1024. Other boot loaders may work also.

 

Don

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@donh and goodoporn:

 

Please note that I wrote about the partition for the boot loader/selector, not the OS. Sure, grub, Acronis, BootMagic and I'm sure many more boot selectors can boot from partitions starting beyond 1024 cyl but in order for them to work youm must place the boot selector itself before the 1024 cyl. In case you are using Mac OS' native boot loader, the boot loader and the OS are on the same partition which should start before that boundary.

 

@Vapor1:

The 1024 boundary is usualy around 8.4 GB from the begining of the disk.

Edited by fprince
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@donh and goodoporn:

 

Please note that I wrote about the partition for the boot loader/selector, not the OS. Sure, grub, Acronis, BootMagic and I'm sure many more boot selectors can boot from partitions starting beyond 1024 cyl but in order for them to work youm must place the boot selector itself before the 1024 cyl. In case you are using Mac OS' native boot loader, the boot loader and the OS are on the same partition which should start before that boundary.

 

@Vapor1:

The 1024 boundary is usualy around 8.4 GB from the begining of the disk.

 

I think this is confusing the issue. The bootloader is usually in the MBR. The bootloader then passes control to the partition you choose.

 

Don

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Without using any external boot loaders, I had my OS X installed on the last partition, far beyond the boundary and it would boot only from the installation DVD.

 

@cbmkgd: the boundary is expressed in cylinders, conversion to GB depends on the geometry of the drive

 

@Vertigo50: BootMagic that comes with Partition Magic is considered to be a good boot-loader, it's even described in the installation guides, yet you can install it on any FAT partition including those non-bootable.

 

@donh:

Not all boot managers work the same way, MBR is only 512 bytes! Please refer to this article for explanation:

http://en.wikipedia.org/wiki/Master_boot_r...m_bootstrapping

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Without using any external boot loaders, I had my OS X installed on the last partition, far beyond the boundary and it would boot only from the installation DVD.

@donh:

Not all boot managers work the same way, MBR is only 512 bytes! Please refer to this article for explanation:

http://en.wikipedia.org/wiki/Master_boot_r...m_bootstrapping

 

The reason it would not boot is probably covered here. http://forum.insanelymac.com/index.php?sho...c=30322&hl=

 

The PC always reads the MBR (first 512) then passes control to what ever is discribed there. I wouldnt bet my pay check but I am prety sure the darwin boot loader will work past 1024. It does need to be a primary partition and active.

 

Don

 

PS

Hey Ramjet, why not do one of your famous copilations on boot problems so people can find them.

Edited by donh
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Without using any external boot loaders, I had my OS X installed on the last partition, far beyond the boundary and it would boot only from the installation DVD.

 

@cbmkgd: the boundary is expressed in cylinders, conversion to GB depends on the geometry of the drive

My first OSX partition, beyond 26GB, is at cylinder 3423.

Edited by cbmkgd
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