Syslinux - Mar 2009 - [PATCH 0/1] v3: Add Diagnostic MBR for trouble-shooting

Changes:

  * If Ctrl key is pressed force load from first hard disk (0x80)

To help users diagnose boot errors, especially with external devices
such as USB flash memory mass-storage, I've created this diagnostic
MBR.

It succinctly reports the values received from the BIOS, locates and
reads the active partition boot sector, reports the magic bytes and
and read-sector error code.

Holding down a shift key during boot will force CHS mode even if LBA is
detected. Holding down a Ctrl key will force loading the boot-sector
from the first hard-disk regardless of the BIOS drive-number in DL.

Detailed information on reported data and usage is in the header
commentary
of mbr/mbr-diag.S; here is an example:

DIAG L D80h C3FFh H10h S3Fh P1 O00000020 MAA55h E00h

which means:
  [L]BA addressing mode (alternative is [C]HS),
  [D]isk 0x80,
  [C]ylinders 0x3FF,
  [H]eads 0x10,
  [S]ectors 0x3F,
  [P]artition active 1,
  [O]ffset to boot-sector 0x00000020,
  [M]agic bytes (of boot-sector) 0xAA55, 
  [E]rror code (from AH=0x42/0x02, int 0x13) 0x00

TJ (1):
  Add Diagnostic MBR for trouble-shooting BIOS boot-order problems.

 mbr/Makefile   |    6 +-
 mbr/mbr-diag.S |  377 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 382 insertions(+), 1 deletions(-)
 create mode 100644 mbr/mbr-diag.S