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Newsgroups: comp.unix.bsd.freebsd.misc Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!solace!news.stealth.net!www.nntp.primenet.com!nntp.primenet.com!netcom.com!gerg From: gerg@netcom.com (Greg Andrews) Subject: Re: 2.1.5-RELEASE sio silo overflows? Message-ID: <gergDxK0FH.AFp@netcom.com> Organization: Movie marquee: THE FLY GODS MUST BE CRAZY ALIENS References: <50i54c$mq7@yama.mcc.ac.uk> <50kb48$9ok@helena.mt.net> <gergDxG5ry.FGo@netcom.com> <512goo$15q@anorak.coverform.lan> Date: Wed, 11 Sep 1996 05:54:53 GMT Lines: 27 Sender: gerg@netcom23.netcom.com brian@awfulhak.demon.co.uk (Brian Somers) writes: >Greg Andrews (gerg@netcom.com) wrote: >: The uart's interrupt trigger is set to *14*??!? > >: Man, I thought people had figured that one out by now. > >: On OS architectures that carry a lot of latency responding >: to hardware interrupts (like a multi-user, multitasking OS), >: a trigger level of 14 is *not* adequate to prevent overflow >: errors. > >[reasoning deleted] > >Ah, but FreeBSD is a multi-user, multitasking OS that doesn't carry much >latency at all ! That's why I can drive a 28.8k modem at a DTR of 115200 >through an 8250 UART :) It must be about a year since I saw my last >serial overflow. > Driving the modem isn't the issue. It's *receiving* data at high speeds that has trouble with interrupt latencies, not sending data. -Greg -- ::::::::::::::::::: Greg Andrews gerg@netcom.com ::::::::::::::::::: Hardware, n.: The parts of a computer system that can be kicked. :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::