From owner-freebsd-hackers@FreeBSD.ORG Fri Apr 9 11:30:09 2004 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 829E516A4CE for ; Fri, 9 Apr 2004 11:30:09 -0700 (PDT) Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by mx1.FreeBSD.org (Postfix) with ESMTP id C3A8343D2D for ; Fri, 9 Apr 2004 11:30:08 -0700 (PDT) (envelope-from ticso@cicely12.cicely.de) Received: from cicely5.cicely.de (cicely5.cicely.de [IPv6:3ffe:400:8d0:301:200:92ff:fe9b:20e7]) (authenticated bits=0) i39IS3US029353 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=OK); Fri, 9 Apr 2004 20:28:07 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (cicely12.cicely.de [IPv6:3ffe:400:8d0:301::12]) by cicely5.cicely.de (8.12.10/8.12.10) with ESMTP id i39IQvhn088293 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 9 Apr 2004 20:26:57 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (localhost [127.0.0.1]) by cicely12.cicely.de (8.12.11/8.12.11) with ESMTP id i39IQu2r014842; Fri, 9 Apr 2004 20:26:56 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: (from ticso@localhost) by cicely12.cicely.de (8.12.11/8.12.11/Submit) id i39IQuKx014841; Fri, 9 Apr 2004 20:26:56 +0200 (CEST) (envelope-from ticso) Date: Fri, 9 Apr 2004 20:26:56 +0200 From: Bernd Walter To: "Louis A. Mamakos" Message-ID: <20040409182655.GO5279@cicely12.cicely.de> References: <20040407170422.GF567@funkthat.com> <20040408024455.GC20138@dhcp01.pn.xcllnt.net> <20040408.123443.101835222.imp@bsdimp.com> <20040409113021.GK5279@cicely12.cicely.de> <200404091801.i39I1uUQ039151@whizzo.transsys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200404091801.i39I1uUQ039151@whizzo.transsys.com> X-Operating-System: FreeBSD cicely12.cicely.de 5.2-CURRENT alpha User-Agent: Mutt/1.5.6i X-Spam-Status: No, hits=-4.9 required=3.0 tests=BAYES_00 autolearn=ham version=2.63 X-Spam-Report: * -4.9 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on cicely12.cicely.de cc: freebsd-hackers@freebsd.org cc: marcel@xcllnt.net cc: ticso@cicely.de cc: atkin901@yahoo.com Subject: Re: polling for sio? 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: Fri, 09 Apr 2004 18:30:09 -0000 On Fri, Apr 09, 2004 at 02:01:56PM -0400, Louis A. Mamakos wrote: > > Those cards are just what they are - cheap. > > They have very small FIFOs and they don't use DMA. > > IRQ sharing makes them even worse than traditional ISA stuff. > > My advise for cost efficient and fast serials is getting USB ones. > > Even noname USB serials do much better then puc(4) based. > > E.g. the FT232BM (uftdi(4)) has 128 bytes send and 384 bytes receive > > buffer plus your USB controller does DMA. > > At best you would add a cheap OHCI card if your onboard USB is UHCI > > based as OHCI is less CPU intensive. > > I used to use 9600 bps serial links on LSI-11/23 systems 20 years ago > to run SLIP over. This was with dumb DL-11 serial adapters on way > slower CPUs and busses than we have today. The difference was a > much lower interrupt latency. You'd think that running serial links > 10 times faster on CPUs that are a few hundred times faster wouldn't > be too hard. I'm not saying that interrupt latency is OK and that it's impossible to get things running with this kind of hardware, but it's very questionable that you have a fast CPU with fast IO bandwidth just to waste cycles for cheap hardware while you can easily get much more efficient hardware for your money. 16550 design is ancient - having them addressed via PCI doesn't change very much. You are also not running your Fastethernet with the same mechanisms as you did with your 10 times slower ISA NIC. -- B.Walter BWCT http://www.bwct.de ticso@bwct.de info@bwct.de