From owner-freebsd-hackers@FreeBSD.ORG Wed Apr 9 06:47:43 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3514E37B401 for ; Wed, 9 Apr 2003 06:47:43 -0700 (PDT) Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by mx1.FreeBSD.org (Postfix) with ESMTP id DF1D643F3F for ; Wed, 9 Apr 2003 06:47:41 -0700 (PDT) (envelope-from ticso@cicely9.cicely.de) Received: from cicely5.cicely.de (cicely5.cicely.de [IPv6:3ffe:400:8d0:301:200:92ff:fe9b:20e7]) by srv1.cosmo-project.de (8.12.9/8.12.9) with ESMTP id h39DlZcx069753 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=OK); Wed, 9 Apr 2003 15:47:37 +0200 (CEST) (envelope-from ticso@cicely9.cicely.de) Received: from cicely9.cicely.de (cicely9.cicely.de [IPv6:3ffe:400:8d0:301:210:5aff:fe30:1c1a]) by cicely5.cicely.de (8.12.9/8.12.9) with ESMTP id h39DlWAL058047 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 9 Apr 2003 15:47:34 +0200 (CEST) (envelope-from ticso@cicely9.cicely.de) Received: from cicely9.cicely.de (localhost [127.0.0.1]) by cicely9.cicely.de (8.12.9/8.12.8) with ESMTP id h39DlVi3095539; Wed, 9 Apr 2003 15:47:32 +0200 (CEST) (envelope-from ticso@cicely9.cicely.de) Received: (from ticso@localhost) by cicely9.cicely.de (8.12.9/8.12.9/Submit) id h39DlTMh095538; Wed, 9 Apr 2003 15:47:29 +0200 (CEST) (envelope-from ticso) Date: Wed, 9 Apr 2003 15:47:28 +0200 From: Bernd Walter To: Harti Brandt Message-ID: <20030409134727.GB95434@cicely9.cicely.de> References: <20030409114957.GN83126@cicely9.cicely.de> <20030409144042.B901@beagle.fokus.fraunhofer.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030409144042.B901@beagle.fokus.fraunhofer.de> X-Operating-System: FreeBSD cicely9.cicely.de 5.0-CURRENT alpha User-Agent: Mutt/1.5.3i cc: hackers@freebsd.org cc: ticso@cicely.de Subject: Re: realtime problem X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: ticso@cicely.de List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 Apr 2003 13:47:43 -0000 On Wed, Apr 09, 2003 at 02:45:07PM +0200, Harti Brandt wrote: > On Wed, 9 Apr 2003, Bernd Walter wrote: > BW>I need a realtime behavour in the (-current) kernel with 1ms > BW>resolution and a presision of 500us. > BW>I thought about these two ways: > BW>- use timeout(9), but it seems that on i386 we only have a > BW> resolution of 10ms. > BW> And I don't know of what presision quality I can expect. > BW> Can the resolution changed to 1ms as we have on alpha? > BW>- attach to the clock service routine. > BW> I asume the presision will be good enough. > BW> But how can I find out the resolution on a given hardware? > BW> > BW>What is the best way to solve the problem? > > You must change HZ by putting > > options HZ=2000 > > or whatever you want in your config file. > > You should also ensure, that you have no miibus ethernet cards in your > system, or comment out the relevant sections in dev/mii that periodically > call the status update stuff. > > I fact I have used a HZ=10000 machine to simulate a 120000 packets/sec > satellite link with good success (jitters are in the order of 300usecs). That's a hopefully information. Did you use a hardclock, timeout(9) or something else? > If you really mean 'real-time' with bounded times for interrupts and so > on, that will be much harder :-) See Terry's mail. Well it's wishfull to have non failures on my requirements, but if it does fail once it is detectable and it only costs a small amount of money - noone will die because of it. If I would need garantied 100% acuracy, then I would spend the money into a microcontroller to do the job. In fact I need it for the programming impulse on writing EPROMs and GALs. GALs are the devices which may need a 1ms programming impulse, but I don't know if there are really devices on the maket which use 1ms. EPROMS are not very sensible on the programming length. I really hate that available burners need DOS or Windows. -- B.Walter BWCT http://www.bwct.de ticso@bwct.de info@bwct.de