From owner-freebsd-hackers Wed Jul 17 10:58:37 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id KAA07081 for hackers-outgoing; Wed, 17 Jul 1996 10:58:37 -0700 (PDT) Received: from etinc.com ([204.141.95.6]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id KAA07068 for ; Wed, 17 Jul 1996 10:58:34 -0700 (PDT) Received: from ppp-089.etinc.com (ppp-089.etinc.com [204.141.95.148]) by etinc.com (8.6.12/8.6.9) with SMTP id OAA24031; Wed, 17 Jul 1996 14:00:18 -0400 Date: Wed, 17 Jul 1996 14:00:18 -0400 Message-Id: <199607171800.OAA24031@etinc.com> X-Sender: dennis@etinc.com X-Mailer: Windows Eudora Version 2.0.3 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: "Michael L. VanLoon -- HeadCandy.com" From: dennis@etinc.com (Dennis) Subject: Re: mitsumi CD-ROM Cc: hackers@freebsd.org Sender: owner-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk >>To no-doubt spurn another wide-eyed debate among the academics, I also >>dont want a bus-mastering controller stealing the bus from my more-critical >>communications in a router-system where disk functions are secondary. > >This makes no sense. The only time a bus-mastering controller >"steals" the bus is when you're doing I/O. An IDE drive not only >steals the bus by implication, but it steals the CPU as well! >Basically, IDE steals the entire machine until the I/O is finished. >At least with a bus-mastering controller, the CPU can run out of the >cache while a disk transfer is in progress. > >I can understand your opinion on this, as stated above. But to think >that you're not getting the bus, and the CPU, stolen, when >bus-mastering would steal only the bus, is a complete >misunderstanding. stealing the bus is stealing the cpu when a router is doing largely transfers from cards. Your cant process packets until you get them. And if the cpu is in a transfer cycle and cant get the bus then its idle. I dont want my packet transfers being interrupted by trivial disk activity. An IDE will only use the CPU when it has it already anyway.....a bus-master makes the system much less predictable and assumes the wrong priorities. db ---------------------------------------------------------------------------- Emerging Technologies, Inc. http://www.etinc.com Synchronous Communications Cards and Routers For Discriminating Tastes. 56k to T1 and beyond. Frame Relay, PPP, HDLC, and X.25 for BSD/OS, FreeBSD and LINUX