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Date: Thu, 9 Jul 2009 20:50:02 GMT
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To: freebsd-bugs@FreeBSD.org
From: Jeff Kletsky <jeff+freebsd@wagsky.com>
Cc: 
Subject: Re: bin/115406: [patch] gpt(8) GPT MBR hangs award BIOS on boot
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The following reply was made to PR bin/115406; it has been noted by GNATS.

From: Jeff Kletsky <jeff+freebsd@wagsky.com>
To: bug-followup@FreeBSD.org, kent@khauser.net
Cc:  
Subject: Re: bin/115406: [patch] gpt(8) GPT MBR hangs award BIOS on boot
Date: Thu, 09 Jul 2009 13:44:44 -0700

 Based on the Intel Extensible Firmware Interface Specification, v 1.10,
 the values present appear to be correct for current drives (anything 
 that exceeds the 500 MB CHS limit).
 It would seem that the issue is compatibility of the BIOS with the Intel 
 spec (assuming that it is the definitive source), not the MBR
 
 On all GUID Partition Table disks a Protective MBR (PMBR) in the first 
 LBA of the disk precedes
 the GUID Partition Table Header to maintain compatibility with existing 
 tools that do not
 understand GPT partition structures. The Protective MBR has the same 
 format as a legacy MBR,
 contains one partition entry of OS type 0xEE and reserves the entire 
 space used on the disk by the
 GPT partitions, including all headers. The Protective MBR that precedes 
 a GUID Partition Table
 Header is shown in Table 11-7. If the GPT partition is larger than a 
 partition that can be
 represented by a legacy MBR, values of all Fs must be used to signify 
 that all space that can be
 possibly reserved by the MBR is being reserved.
 
 Source:
 http://www.intel.com/technology/efi/efiagree.htm
 http://download.intel.com/technology/efi/docs/EFI_110.zip -- Page 11-14 
 (374/1084)
 
 This notwithstanding, http://www.freebsd.org/cgi/query-pr.cgi?pr=133493 
 may still be part of the problem for the OP's systems.