Re: Which processor mode?

[Robert Weber <Robert.Weber@xxxxxxxxxxxx>]

> 
> So to summarize, yes Long mode *can* run 32 bit apps (using
> compatibility mode), or native 64-bit apps. 

Then I assume the os is compiled without the needed REX prefixes that
address 64 bit registers.  This way, users can choose compatibilty mode
in the bios, and the os will work fine with 32 bit code as well.  But in
the case that they want *THEIR* code to access the larger register space,
they can choose 64-bit only mode and the os apps will simply ignore the
larger register space.

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