machine won't start

Tomas Bodzar tomas.bodzar at
Wed Jul 4 10:51:53 PDT 2012

On Wed, Jul 4, 2012 at 7:31 PM, Matthew Dillon
<dillon at> wrote:
>     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.
>                                                 -Matt

There was interesting debate before couple od days/weeks on OpenBSD
about support for disks larger than 2TB. It turned out that they can
be used just fine without GPT, but multiboot capability is mostly lost
as job is done in disklable (their fdisk can't do that)

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