From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 10 Apr 2003 20:24:43 +0100 (BST) Received: from p508B62A5.dip.t-dialin.net ([IPv6:::ffff:80.139.98.165]:7079 "EHLO dea.linux-mips.net") by linux-mips.org with ESMTP id ; Thu, 10 Apr 2003 20:24:42 +0100 Received: (from ralf@localhost) by dea.linux-mips.net (8.11.6/8.11.6) id h3AJOUk01954; Thu, 10 Apr 2003 21:24:30 +0200 Date: Thu, 10 Apr 2003 21:24:30 +0200 From: Ralf Baechle To: Mike Uhler Cc: Jun Sun , linux-mips@linux-mips.org Subject: Re: way selection bit for multi-way cache Message-ID: <20030410212430.A519@linux-mips.org> References: <20030410110527.E9002@mvista.com> <200304101850.h3AIorK11089@uhler-linux.mips.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <200304101850.h3AIorK11089@uhler-linux.mips.com>; from uhler@mips.com on Thu, Apr 10, 2003 at 11:50:53AM -0700 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 1974 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: ralf@linux-mips.org Precedence: bulk X-list: linux-mips On Thu, Apr 10, 2003 at 11:50:53AM -0700, Mike Uhler wrote: > I can't comment on anything but MIPS32 and MIPS64 CPUs, but the > MIPS32 and MIPS64 standard is to use the bits above the index field > to specify the way. See the figure entitled "Usage of Address Fields > to Select Index and Way" in the CACHE instruction description of the > MIPS32 and MIPS64 Architecture for Programmer's manuals. The question came up between Jun and me when revising the way of handling multi-way caches. There is the MIPS32 / MIPS64 way of selecting the cache way - but that scheme was originally already introduced by the R4600. The second somewhat less common scheme is using the lowest bits of the address. That was originally introduced with the R10000 but a few other processors such as the R5432 and the TX49 series are using it as well. Unfortunately there has been way to much creativity (usually a positive property but ...) among designers so this posting is an attempt to achieve completeness. Ralf