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From: ephraim@wang.UUCP (pri=8 Ephraim Vishniac x76659 ms1459)
Newsgroups: net.micro.mac
Subject: Re: Booting from HFS disk on Mac 512
Message-ID: <773@wang.UUCP>
Date: Mon, 17-Mar-86 08:13:55 EST
Article-I.D.: wang.773
Posted: Mon Mar 17 08:13:55 1986
Date-Received: Wed, 19-Mar-86 04:07:23 EST
References: <385@gould9.UUCP>
Organization: Wang Labs, Lowell MA
Lines: 19

>     Build an HFS 400kb disk (using option-initialize under 'Erase Disk')
> 
>     Install System 3.1.1, Finder 5.2, HardDisk 20 1.1a (off of the
>     12/85 software supplement).
> 
>     Try to boot off of a Mac 512.
> 
> The result is Sad Mac code #F0064
> 
> It all works if the disk is non-HFS.  I presume the "HD20" patches don't
> get installed soon enough in the boot process, and that HFS volumes can
> be the boot disk only on a machine (e.g. Plus) with HFS in ROM.
> -- 
Exactly right, Joel.  The Mac first has to find and load the system file
on the startup floppy, then execute the patches (PTCH) resources in it.
One of these (PTCH 105) opens the Hard Disk 20 file and executes the
patches it finds there (0, 1, and 2).  HFS isn't running until all this
has happened.  Also, the "signature bytes" in an HFS volume header are
different, so the 64K roms will think it's a non-Mac diskette immediately.