*BSD News Article 77932


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From: brian@awfulhak.demon.co.uk (Brian Somers)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: 2.1.5-RELEASE sio silo overflows?
Date: 10 Sep 1996 02:37:28 +0100
Organization: Coverform Ltd.
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References: <50i54c$mq7@yama.mcc.ac.uk> <50kb48$9ok@helena.mt.net> <gergDxG5ry.FGo@netcom.com>
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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.

--
Brian <brian@awfulhak.demon.co.uk>
Don't _EVER_ lose your sense of humour....