From owner-freebsd-hardware Sat Jun 29 00:31:23 1996 Return-Path: owner-hardware Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id AAA14253 for hardware-outgoing; Sat, 29 Jun 1996 00:31:23 -0700 (PDT) Received: from genesis.atrad.adelaide.edu.au (genesis.atrad.adelaide.edu.au [129.127.96.120]) by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id AAA14248 for ; Sat, 29 Jun 1996 00:31:20 -0700 (PDT) Received: from msmith@localhost by genesis.atrad.adelaide.edu.au (8.6.12/8.6.9) id QAA20648; Sat, 29 Jun 1996 16:49:40 +0930 From: Michael Smith Message-Id: <199606290719.QAA20648@genesis.atrad.adelaide.edu.au> Subject: Re: muliport boards - building a PPP dialup server To: jparnas@jparnas.cybercom.net (Jacob M. Parnas) Date: Sat, 29 Jun 1996 16:49:40 +0930 (CST) Cc: chuckr@glue.umd.edu, Kevin_Swanson@BLaCKSMITH.com, freebsd-hardware@freebsd.org In-Reply-To: <199606281933.PAA04484@jparnas.cybercom.net> from "Jacob M. Parnas" at Jun 28, 96 03:33:24 pm MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-hardware@freebsd.org X-Loop: FreeBSD.org Precedence: bulk Jacob M. Parnas stands accused of saying: > > These days, a multiboard should at least do 115200baud in my opinion. At > least it can be competitive with modems. 8x115200baud is still only 1/8 > MB/sec and 16x115200 is only 1/4 MByte/sec. Not exactly fast. Fast has nothing to do with it. Interrupt rates do. You should sit down and read some of the stuff that Bruce Evans has posted on the subject over the years; most particularly his analysis of where the actual load in handling serial ports comes from. Some key points : - A 486 can service around 40,000 ISA interrupts per second, assuming minimal interrupt processing time. - Most of the CPU overheard in handling serial in/output is in the tty layer. > Jacob -- ]] Mike Smith, Software Engineer msmith@atrad.adelaide.edu.au [[ ]] Genesis Software genesis@atrad.adelaide.edu.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control (ph/fax) +61-8-267-3039 [[ ]] Collector of old Unix hardware. "Where are your PEZ?" The Tick [[