amd64 newbie question [32 bit compatibility]

Peter Jeremy peterjeremy at
Sun Mar 25 19:11:12 UTC 2007

On 2007-Mar-25 06:09:43 +0200, Peter Ulrich Kruppa <ulrich at> wrote:
>Is there any kind of documentation about this "32 bit 
>compatibility layer"? Do I have one? Does it work and if yes, 

When in 64-bit mode, amd64 family chips can execute 32-bit code in much
the same way as the x86 chips can execure 16-bit code via VM86.  This
is referred to as "Compatibility Mode" in the AMD documentation.  There
is AMD documentation on this but I can't quickly find the details.

FreeBSD supports 32-bit compatibility mode by default:  When the ELF
loader is handed a 32-bit executable, it starts a compatibility mode
process and uses 32-bit shared libraries (/usr/lib32, /usr/local/lib32,

There are still some rough edges - in particular, 32-bit threaded
programs don't work.

Peter Jeremy
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