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Re: Error in Installation Guide, amd64 for EM64T?

Tapio Lehtonen wrote:

> Installation guide says in Chapter 2:
> "If your system has a 64-bits AMD64, Intel EM64t or Intel Core 2 Duo
> processor, you will probably want to use the installer for the amd64
> architecture instead of the installer for the (32-bits) i386
> architecture."
> Is this really true? What is installer for i64 good for, then?
> Or does Intel have in addtition to EM64t prosessors another kind of
> 64-bit prosessor that is not compatible with amd64?

Bingo, the chip for "ia64" is Intel's _original_ 64-bit processor called
Itanium.  It is incompatible with code written for i386 (unlike AMD64
and EM64t, which were specifically created to be compatible with 32-bit
x86 architecture), although I think it can run x86 code through an
emulator.  For this reason it never became very popular.  (The fact that
it was absurdly expensive and hard to write an optimizing compiler for
didn't help.)

Perhaps the section of the installation guide for ia64 should
specifically say something like "This architecture is NOT suitable for
the Intel EM64t or Intel Core 2 Duo chips -- for those use the 'amd64'
architecture."  It may already do so, I haven't checked.

It's an unfortunate accident of history, which we now have to live with,
that the Debian arch name for AMD64/EM64t is "amd64" -- it was
originally going to be the brand-generic "x86-64" but that was rejected
after a big fight for some reason that I don't recall.  Then later Intel
came out with an AMD64-compatible chip.

To summarize,

Debian arch		Chipsets
-----------		--------
i386			x86 (for x strictly greater than 3) [0]
ia64			Intel's Itanium 64-bit chip
amd64			x86-compatible 64-bit chips (AMD64/EM64t/etc.)

[0] Debian no longer supports real 80386 chips because the GNU C++
library uses inline assembly (or something like that) that isn't
supported on them.  (I forget whether or not 80386 is supported in
Sarge; it definitely was in Woody and will not be in Etch.)  Since APT
is written in C++, a Debian installation on 80386 would be essentially


Kevin B. McCarty <kmccarty@princeton.edu>   Physics Department
WWW: http://www.princeton.edu/~kmccarty/    Princeton University
GPG: public key ID 4F83C751                 Princeton, NJ 08544

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