Path: utzoo!attcan!uunet!lll-winken!ncis.llnl.gov!ncis!helios.ee.lbl.gov!pasteur!ucbvax!decwrl!labrea!rutgers!rochester!pt.cs.cmu.edu!cadre!pitt!crew
From: crew@pitt.UUCP (Al Crew)
Newsgroups: comp.os.minix
Subject: Re: Help! Minix 1.3 & PS/2 Model 80
Message-ID: <4463@pitt.UUCP>
Date: 18 Jan 89 04:06:31 GMT
References: <1023@uvm-gen.UUCP> <1906@ast.cs.vu.nl>
Reply-To: crew@vax.cs.pittsburgh.edu.UUCP (Al Crew)
Organization: Univ. of Pittsburgh Computer Science
Lines: 19

On the PS/2 problems, quoting the PS/2 Technical Reference:

"Service routines must not attempt to end the interrupt sequence (EOI)
until it has reset the interrupt line of the device being serviced."

I didn't actually look up the bit pattern, but I assume the "ENABLE"
in line 1888 of the book is the 8259A's EOI command.

This could be a problem in the Minix environment where the interrupt
would not be cleared until the floppy task is dispatched.

Also, interestingly, the PS/2 will not allow you to set the PIC up in
edge-sensitive mode (even accidentally):

"The interrupt control circuitry of the system board prevents
setting the controller to the edge-sensitive mode by blocking positive
edge-sensitive commands to the interrupt controllers."

(Yes, I did look up the bit pattern "ENABLE" is EOI.)