*BSD News Article 24164


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From: vandys@cisco.com (Andrew Valencia)
Newsgroups: comp.os.386bsd.questions
Subject: Re: ISA strayintr 7 - please help!!
Date: 18 Nov 93 02:36:59 GMT
Organization: cisco Systems
Lines: 18
Message-ID: <vandys.753590219@cisco.com>
References: <2c6nga$2e8@darkstar.UCSC.EDU> <wilko.753391395@spoetnix.idca.tds.philips.nl> <2cafgi$rqs@olivaw.apanix.apana.org.au> <2cecj3$g30@usenet.mcs.kent.edu>
NNTP-Posting-Host: glare.cisco.com

In <2cecj3$g30@usenet.mcs.kent.edu> borsburn@mcs.kent.edu (Bret Orsburn) writes:

>In article <2cafgi$rqs@olivaw.apanix.apana.org.au> hart@apanix.apana.org.au (Leigh Hart) writes:
>>Printer ports usually have no need for interrupt routines because they
>>very rarely are input devices.
>Sorry if I'm missing some contextual subtlety here, but this statement is
>nonsense. Lots of output devices use interrupts.

You're both right.

In the case of PC parallel ports, many interface cards do not interrupt
reliably, thus polling drivers were written.  The "interruptless" LP
driver uses some clever adaptive counters to tune itself to your port
and printer.  Lots of other output devices (the transmit side of
RS-232, for instance) do indeed use interrupts even when only operating
as output devices.

						Andy