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To: linux-kernel@vger.kernel.org
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Where is it written?
Date: 12 Nov 2000 21:28:29 -0800
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In-Reply-To: <20001110184031.A2704@munchkin.spectacle-pond.org> <20001111163204.B6367@inspiron.suse.de> <20001111171749.A32100@wire.cadcamlab.org> <20001112132328.C2366@athlon.random>
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Followup to:  <20001112132328.C2366@athlon.random>
By author:    Andrea Arcangeli <andrea@suse.de>
In newsgroup: linux.dev.kernel
> 
> I think it doesn't worth to break binary compatilibity at this late stage.
> 
> > design such.)  One issue: ideally you want to use 64-bit regs on AMD
> > Hammer for long longs, but then you leave out all legacy x68s. :(
> 
> We can't in compatibilty mode because the rex regs are available _only_ in
> 64bit mode and even assuming the hardware would support that I would not
> recommend that since as you said that binary would not run anymore on any other
> x86 so causing pain.  Recompiling a program with native x86-64 gcc 64bit (that
> uses the 64bit ABI) is the right way to go in that case (64bit mode uses 1
> 64bit register for long long as all other 64bit architectures of course).
> 

Well, you *could* run REX32, but REX32 is not x86 (x86 code doesn't
run in REX32 mode, and REX32 code doesn't run on an x86.)

	-hpa
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<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
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