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From: Martin Str|mberg <ams AT speedy DOT ludd DOT ltu DOT se>
Subject: Re: 64 bit access under DOS?
Newsgroups: comp.os.msdos.djgpp
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Date: 13 Sep 2006 09:29:52 GMT
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To: djgpp AT delorie DOT com
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Rod Pemberton <do_not_have AT bitfoad DOT cmm> wrote:
> "Martin Str|mberg" <ams AT speedy DOT ludd DOT ltu DOT se> wrote in message
>> Unfortunately AMD64 instructions are only available in long 64-bit
>> (non-compatibility) mode and in long mode vm86 mode isn't supported,
>> so this won't happen.
>>

> Ah, good, someone who is familiar with 64-bit mode.

Not that familiar, but I've read the specification.

> What you're saying it that there are no override prefixes to access the
> 64-bit instructions in 32-bit mode.  Correct?

Yes.

> Is there a method to switch into and out of 64-bit mode safely while running
> under 32-bit protected mode (DPMI or Windows)?

If you're the OS, yes. IIRC, that how you get to 64-bit mode. You have
to go RM->PM32->PM64.


Right,

						MartinS