Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750783AbXAUO7p (ORCPT ); Sun, 21 Jan 2007 09:59:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750696AbXAUO7p (ORCPT ); Sun, 21 Jan 2007 09:59:45 -0500 Received: from 1wt.eu ([62.212.114.60]:2117 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783AbXAUO7o (ORCPT ); Sun, 21 Jan 2007 09:59:44 -0500 Date: Sun, 21 Jan 2007 15:58:17 +0100 From: Willy Tarreau To: Grzegorz Ja?kiewicz Cc: Johannes Stezenbach , Theodore Tso , Joe Barr , Linux Kernel mailing List Subject: Re: Serial port blues Message-ID: <20070121145817.GE31780@1wt.eu> References: <1169242654.20402.154.camel@warthawg-desktop> <20070120173644.GY24090@1wt.eu> <20070121055456.GC27422@thunk.org> <20070121070557.GB31780@1wt.eu> <20070121140421.GA13425@linuxtv.org> <2f4958ff0701210650w4fa0138di6a5026de8a0823dc@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2f4958ff0701210650w4fa0138di6a5026de8a0823dc@mail.gmail.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1337 Lines: 26 On Sun, Jan 21, 2007 at 03:50:32PM +0100, Grzegorz Ja?kiewicz wrote: > funny, how even very fast box can be useless for such activities with modern > kernels, such as linux. After all, serial ports don't require too much > horsepower to be highly accurate. > >From designer perspective, I would rather go for uC solution in his case. > That is, design and build fairly simple board - based on atmega AVRs. 16mhz > 8bit chip can do so much better compared to N gigs mhz box running "modern" > operating system, these days.... It is true, but the point is not "modern" vs "ancient" OS, it's "multitasking" vs "monotasking" kernel. If your program does the busy loop, you'll get a very high accuracy at the expense of burning watts polling one bit one billion times a second waiting for a change every millisecond. 18 years ago, I wrote a soft-only 8250 emulator to connect my second 8088 to the first one's serial port at 19200 bauds. At this time, waiting for a change only took a few hundred cycles and the busy loop was the default mode of the OS anyway. Things have changed since. Willy - 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/