*BSD News Article 93257


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From: token@cip.informatik.uni-wuerzburg.de (Matthias Buelow)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: sio?: silo overflow
Date: 9 Apr 1997 13:46:38 GMT
Organization: University of Wuerzburg, Germany
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Hello folks,

I've been configuring a 486dx2-80/8MB to route tcp/ip between a winNT
box connected via ethernet, an amiga/060 connected by slip on cuaa1
(115200 bps) and a modem (28k8, on cuaa0, speed 115200) which connects
the stuff with the outer world using pppd.  The operating system is
FreeBSD 2.2.1R.  It all works nicely except some occasional messages
syslog spits all over the root console explaining that the sio-driver
detected some silo overflow on the serial ports.  Both serial ports
are 16550A and have a fifo.  The one that attaches slip to the amiga
gets some more overflows (7 so far in a few hours yesterday) while the
modem port is almost neglectable (2 overflows).  We had some more trouble
when using the onboard ports (we disabled & replaced them with a board)
especially that the device kept sending junk data when the modem was
already off or even disconnected (we discovered that with minicom and
ppp-term).  That doesn't happen anymore with the seperate ports on the
i/o-board.
I've looked up the driver source and saw that the message is printed when
the serial control-line indicates a data register overrun.  I'm not very
familiar with serial port programming on PCs so I don't know where exactly
the problem is.  When does this overflow happen?  On incoming or outgoing
data?  The manpage just says "problem with the interrupt handler" or
similar.  Does it indicate some weak hardware or can I fix it?  It's not
really a problem but somewhat annoying.

-- 
	--token

``Good morning, doctors. I have taken the liberty of removing Windows 95 from
  my harddrive.''        - Arthur C. Clarke, imagining the first words of HAL