Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 16 Oct 2002 07:40:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 16 Oct 2002 07:40:19 -0400 Received: from delta.ds2.pg.gda.pl ([213.192.72.1]:22998 "EHLO delta.ds2.pg.gda.pl") by vger.kernel.org with ESMTP id ; Wed, 16 Oct 2002 07:40:18 -0400 Date: Wed, 16 Oct 2002 13:46:31 +0200 (MET DST) From: "Maciej W. Rozycki" To: "H. Peter Anvin" cc: linux-kernel@vger.kernel.org Subject: Re: mapping 36 bit physical addresses into 32 bit virtual In-Reply-To: Message-ID: Organization: Technical University of Gdansk MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1188 Lines: 26 On 15 Oct 2002, H. Peter Anvin wrote: > Oh no, the x86 madness is spreading!!!! > > (It's depressing this happening on a MIPS system, which has been 64 > bits since who-knows-when...) Yep, but the reasons are different -- the embedded people are paranoid on cutting away any possible bit of silicon and, admittedly, they are right, to some extent. Why do they need 36-bit physical addressing in 32-bit cores remains a mystery to me, though, yet the MIPS32 ISA spec permits up to 36 bits (implementation-specific) here. Even more interesting is why an implementation chose mapping of I/O devices there -- it's usually easier for an OS to have them mapped within the low 29-bit address space where they can be accessed bypassing the TLB. -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available + - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/