machine won't start

Matthew Dillon dillon at
Wed Jul 4 10:31:46 PDT 2012

    Normally this issue can be fixed by setting the BIOS to access the
    disk in LBA or LARGE mode.  The problem is due to a bug in the BIOS's
    attempt to interpret the slice table in CHS mode instead of logical
    block mode.  It's a BIOS bug.  These old BIOS's make a lot of assumptions
    w/regards to the contents of the slice table, including making explicit
    checks for particular OS types in the table.

    I've only ever seen the problem on old machines, and I've always
    been able to solve it by setting the BIOS access mode.

    I've never, ever found a slice table format that works properly across
    all BIOSs.  At this juncture we are using only newer (newer being 'only'
    25+ years old) slice table formats (aka LBA layouts and using proper
    capped values for hard drives that are larger than the 32-bit LBA layout
    can handle).

    Ultimately we will want to start formatting things w/GPT, but that opens
    up a whole new can of worms... old BIOSes can explode even more easily
    when presented with a GPT's compat slice format, at least as defined
    by GPT.  Numerous vendors such as Apple modified their GPT to try
    to work around the even larger number of BIOS bugs related to GPT
    formatting than were present for the older LBA formatting.

    I consider it almost a lost cause.


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