Subject: mouse interrupts
To: None <>
From: Michael L. VanLoon -- Iowa State University <>
List: current-users
Date: 05/10/1994 23:27:50
In icu.h it mentions the interrupts being in a certain priority.  How
exactly is this "priority" determined?  Is this just the priority
given to the interrupt controller, or something more complex that
tells the low-level interrupt handler to handle interrupts in a
certain order?

Interrupt 5 is almost at the bottom of the list.  This, in my system,
is the port containing my Logitech bus mouse.  I assume the reason for
putting it down there is to give the parallel ports relatively low
priority (5 being a common IRQ for LPT2 on DOS machines), which seems
like a reasonable thing to do.

But, under heavy use (modem going, some paging, etc.) the mouse can
sometimes get way behind on my system.  It's like moving the mouse,
then having to sit and wait for several seconds to see anything at all
happen.  In contrast, no matter what is happening on my DECstation at
work, the mouse is always smoooooooth and updated instantly whenever
it moves.

Would changing the "priority" of the mouse from near the bottom, to
right up near the top after the keyboard interrupt be a reasonable way
to maybe get a bit more smoothness?  I know this isn't a simple thing
to do since the mouse could potentially be found on several different
interrupts, depending on the model and manufacturer.  In addition, I
understand the X server actually has to receive the mouse movements
and write them to the video card.  But, maybe some cryptic little bit
in config could figure which port you wanted a mouse on and lift that
up in priority when you built a kernel.

In the interest in aesthetics and ergonomics, if this were a workable
way to get better mouse responsiveness, it might be worth playing with
a bit.

 Michael L. VanLoon                 Iowa State University Computation Center                    Project Vincent Systems Staff
  Free your mind and your machine -- NetBSD free Un*x for PC/Mac/Amiga/etc.