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Subject: Re: 2.7 block ramblings (was Re: DMA for ide-scsi?)
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Matt Domsch <Matt_Domsch@dell.com>
Cc: Jeff Garzik <jgarzik@pobox.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Sun, 14 Sep 2003 23:26:54 +0100
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On Sad, 2003-09-13 at 17:11, Matt Domsch wrote:
> system-unique disk signature to the boot disk (int13 device 80h)
> "BOOT" or something - we've got 4 bytes available in the msdos label
> for it

int 13 is still available during the 16bit boot up phase of the kernel.
It does strike me as playing with fire, but an alternative approach
might work. Read the first 4K off the boot disk, stuff it somewhere 
temporary and then in 32bit compare it with the disk starts..