Path: utzoo!utgpu!watmath!mks!alex
From: alex@mks.UUCP (Alex White)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Interrupt/Exception Confusion on 80286
Summary: Reprogram the 8259 chip
Keywords: 80286, Interrupts, Protected Mode
Message-ID: <539@mks.UUCP>
Date: 4 Nov 88 14:18:54 GMT
References: <384@rondo.randvax.UUCP>
Organization: Mortice Kern Systems, Waterloo, Ont.
Lines: 14

In article <384@rondo.randvax.UUCP>, edhall@randvax.UUCP (Ed Hall) writes:
> When running an 80286 in protected mode (and for some limited cases
> in real mode) it is possible to generate exceptions with vector numbers
> between 0x8 and 0xf.  Now, on a PC/AT, COM1 is at INT 0xc--which is
> the INT for a stack overflow.  Just how do you tell the two apart?
You re-program the first 8259 interrupt chip to point the first 8 hardware
interrupts to some other base location.
The second interrupt chip is already programmed to point elsewhere - it
was added for the AT, but they had to leave the first chip at the same
location because thats how they did it on the pc.
> 
> Of course, the INTEL 80286 reference says all over it that INT 0x0 to
> INT 0x1f are ``reserved by INTEL.''
And all those idiots at IBM which ignored this should be shot.