Date: Thu, 9 Jul 2009 20:50:02 GMT From: Jeff Kletsky <jeff+freebsd@wagsky.com> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/115406: [patch] gpt(8) GPT MBR hangs award BIOS on boot Message-ID: <200907092050.n69Ko2VH099379@freefall.freebsd.org>
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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.
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