From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263011AbTDFPWQ (for ); Sun, 6 Apr 2003 11:22:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263012AbTDFPWQ (for ); Sun, 6 Apr 2003 11:22:16 -0400 Received: from pc2-cwma1-4-cust86.swan.cable.ntl.com ([213.105.254.86]:22670 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S263011AbTDFPWP (for ); Sun, 6 Apr 2003 11:22:15 -0400 Subject: Re: [PATCH] take 48-bit lba a bit further From: Alan Cox To: John Bradford Cc: Jens Axboe , Linux Kernel Mailing List In-Reply-To: <200304061332.h36DWnaD000165@81-2-122-30.bradfords.org.uk> References: <200304061332.h36DWnaD000165@81-2-122-30.bradfords.org.uk> Content-Type: text/plain Content-Transfer-Encoding: 7bit Organization: Message-Id: <1049639724.962.7.camel@dhcp22.swansea.linux.org.uk> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.2 (1.2.2-5) Date: 06 Apr 2003 15:35:25 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sul, 2003-04-06 at 14:32, John Bradford wrote: > Then, don't we want to be using 48-bit lba all the time on compatible devices > instead of falling back to 28-bit when possible to save a small amount of > instruction overhead? (Or is that what we're doing already? I haven't really > had the time to follow this thread). The overhead of the double load of the command registers is microseconds so it is actually quite a lot, especially since IDE lacks TCQ so neither end of the link is doing *anything* useful. SCSI has similar problems on older SCSI with command sending being slow, but the drive is at least doing other commands during this.