Re: [9fans] Re: random moving of cursor arrow

[David Presotto <presotto@closedmind.org>]

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We had a long history of 16[54]xx chips with buggy fifos
and/or unchangeable length fifos.  At 1200 baud, these
guys used to delay mouse actions 1/7 of a second during
a sweep and as much as 1/4 second at the end of the sweep.
The sweep delay was barely perceptible but the mouse movement
just as you were taking your hand off the mouse bothered
people.  We had similar problems with uarts on MIPS/SGI
machines.  All those machines should have died years ago,
but since I don't normally use a serial port mouse (all ours are
PS/2) I just haven't bothered.  I'll make fifo on the default
for serial mice.

However, that really doesn't explain what's going on.  Unless the
people seeing these problems are on sub 100 megahz machines, we're
really screwing up if we can't keep up with 120 or 240 interrupts
per second.  Something must have broken when we changed to a common
model for all the uarts (or changed the scheduler).  I'll go into
work today and bang at some machines and see if I can recreate/fix
the problem.  I'm back for a way or two to rest up and serial
ports are about as restful as it gets.

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From: C H Forsyth <forsyth@vitanuova.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Re: random moving of cursor arrow
Date: Sat, 26 Jul 2003 09:37:12 +0100
Message-ID: <29ce300d69819f673d96bbd7d9ae9302@vitanuova.com>

>>I used to avoid the fifo for mice because it made the mouse jerky.

i never really understood that: i switched on the uart fifo at the start on a system
i did and it handled a mouse without fuss.