Subject: Re: Dramatic Serial Port Speed Reduction
To: Robert Shady <>
From: Michael L. VanLoon -- Iowa State University <>
List: current-users
Date: 03/22/1994 09:50:37
>Has anybody else noticed a dramatic speed loss since Chris fixed the Com
>driver?  I am noticing a STEADY decrease of ~300 CPS...
>	-- Rob

I'm not sure if this is related, but I noticed the old default of
FIFO_TRIGGER_4 has changed to FIFO_TRIGGER_14 on serial port setup.
My machine simply does not have the speed to catch the interrupt and
process it before those last two characters are gone at 38400.  I
simply can't run my serial port above 19200 with the trigger set at
14 without missing characters.

The point of the fifo is to give the machine time to process things
after receiving an interrupt, and before it has time to finish
servicing it.  Can we have the old default setting of 4 again?  Either
that, or could we have like FreeBSD where it's just FIFO_TRIGGER in
the com.c and is only assigned a level if you don't specify your
preferred trigger level in your config file (options FIFO_TRIGGER=
FIFO_TRIGGER_4, or something to that effect).


 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.