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Author Topic: Are boot0/chain0/boot1h really necessary?  (Read 4875 times)

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tempolo

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Are boot0/chain0/boot1h really necessary?
« on: June 14, 2009, 11:14:55 PM »
As much as I understand the boot process so far, boot0/chain0 are only there to load boot1h from the start of a partition.
boot1h in turn is able to read HFS+ to load a file called "boot" from there.
That's all these do.

Hence, wouldn't it be also possible to use some other PC boot loader and tell it to load "boot" from a NTFS or FAT32 volume instead? "boot", after all, has to provide all its own HFS reading code anyways, doesn't it, so it shouldn't matter how it got loaded, does it?
And then, I'd expect, that "boot" scans all available drives and partitions on its own.

Would that work? If not, where am I wrong in my assumptions?


Kabyl

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Re: Are boot0/chain0/boot1h really necessary?
« Reply #1 on: June 14, 2009, 11:19:27 PM »
Correct, but you need to load it at a specific address in memory: 0x2000:0x0200 or 0x20200.

tempolo

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Re: Are boot0/chain0/boot1h really necessary?
« Reply #2 on: June 14, 2009, 11:59:10 PM »
Cool.

I've never dealt with Windows and boot loaders before (I'm a Mac guy, entirely). Looking at the default Windows MBR code, it looks like it is loading a NTLDR file directly, is that correct? And I guess that this NTLDR is then also reading the boot.ini where one can add other Windows partitions or configurations, correct?

I ask because I am still pondering the "boot strap" I wrote yesterday about: I like to to be able to load chameleon from a default Windows installation as it comes with a Asus 1008HA, with doing as little changes to the existing setup as possible. So I imagine I could maybe write a simple loader that gets loaded by the NTLDR via boot.ini, and which loads the chameleon "boot" file and runs it (both files residing on the Windows C: partition). Would that make sense? Or is there an easier way?

« Last Edit: June 15, 2009, 12:02:04 AM by tempolo »

Lord Anubis

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Re: Are boot0/chain0/boot1h really necessary?
« Reply #3 on: June 15, 2009, 12:52:31 AM »
You want to have diff settings in the ini file to kickoff Chameleon and then choose between the win and mac os? From what I know of is that NTLDR check the filesystem before kicking the OS off.

What about installing chameleon on a small < 1GB HFS partition at the end of your HD, with also an OSX partition behind your org Win partition?

MBR replaced by boot0
org win part
org win install part
mac osx part
....
Chameleon part.
Quicksilver 2002 Case - GB EP45-DS3P - 8Gb Kingston mem. - Q6600 - Asus 7300GT Silent 512Mb - 6 SATA drives - 1 IDE drives ( using F12/Chameleon for booting, not visible in OSX ) - 1 external Sata Samsung DVD - OSX 10.6.8 server retail - Chameleon 2.0RC1 + Cartri Bios

tempolo

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Re: Are boot0/chain0/boot1h really necessary?
« Reply #4 on: June 15, 2009, 08:57:27 AM »
Dear Lord,

There is no room to add another partition on the Asus 1008HA because it uses MBR for partitioning, and it has already reserved four partitions (C: for Windows, D: is empty and used for OSX, next one for system restore, last one an EFI part for flash ROM updates).

So I am looking for a clean way to install Chameleon without messing up the default installation too much.

The suggested default install methods  for Chameleon, when installing from Windows, would require me to store the "boot1h" part of the boot loader in the 2nd partition, the one for OSX, wouldn't it? Or where would it go?

(later)

Looks like this could be a solution: http://www.insanelymac.com/forum/index.php?showtopic=160746

« Last Edit: June 15, 2009, 12:53:13 PM by tempolo »

thorazine74

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Re: Are boot0/chain0/boot1h really necessary?
« Reply #5 on: June 15, 2009, 01:08:04 PM »
From what I know boot0 goes into the disk mbr and boot1h into OS X's partition bootsector. boot0 is not required but boot1h needs to be there to find the boot file.
I'm not sure what you are trying to achieve but if you keep the mbr untouched everything else would go in os x partition so if you wipe that partition you can return to original state.
For installing for windows in any case you need to put the boot file in the HFS partition, you would need HFS write access from windows to do that (MacDrive).
Mac OS X 10.5.6 Retail (Updated to 10.5.7) with Chameleon 2.0 RC1+BootIt NextGen 1.86 (MBR Single Drive)
Gigabyte 73PVM-S2H + C2D + 2 Gb
2 SATA HD (AppleAHCIport.kext) + 1 PATA DVD+RW (DarwinATAPort.kext)
Realtek ALC889 (VoodooHDA.kext)
Geforce 8600GTS (EFI String) PS/2 M & KB: VoodooPS2.kext