Path: utzoo!attcan!uunet!tektronix!pogo!darrellm
From: darrellm@pogo.GPID.TEK.COM (Darrell McGinnis)
Newsgroups: comp.sys.ibm.pc
Subject: Re: IRQ numbers
Summary: IRQ 5 for AT's only.
Keywords: LPT IRQ interrupt
Message-ID: <5835@pogo.GPID.TEK.COM>
Date: 18 Aug 88 17:03:46 GMT
References: <15@ <16800339@clio>
Reply-To: darrellm@pogo.GPID.TEK.COM (Darrell McGinnis)
Organization: Tektronix, Inc., Wilsonville,  OR.
Lines: 23



>lpt2 uses IRQ5 traditionally.
>
>			Mike Berger
>

This is true only for AT type machines.
Original PC's and XT's (pronounced 8088/86) use IRQ 5
for hard drives and provided no IRQ for LPT 2.

Some of the early LPT ports out there have implemented the LPT IRQ
wrong anyway. The problem is associated with the differences in an
'edge triggered' mode and  a 'level triggered' mode.

AST Superpak software has a print spooler that will really
use the LPT IRQ when specified. (If the LPT port you use has
implemented IRQs in the correct way.

Much of the spooler software available uses the timer IRQ to 
periodically check the LPT port for non-BUSY condition.

dsm.