From owner-freebsd-stable  Sun Mar 11  0:15:42 2001
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Date: Sun, 11 Mar 2001 10:15:18 +0200 (IST)
From: Roman Shterenzon <roman@harmonic.co.il>
To: Rich Wales <richw@webcom.com>
Cc: freebsd-stable@FreeBSD.ORG
Subject: Re: Silo overflows
In-Reply-To: <20010304065203.30478.richw@wyattearp.stanford.edu>
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I *think* that when I had this problem on a ThinkPad laptop, having 
0x00008 | 0x20000 (from sio(4)) solved the problem, though, reading
through source, I don't understand why, so it may be a coincidence.

On Sat, 3 Mar 2001, Rich Wales wrote:

> I'm running 4.2-RELEASE on an 800-MHz Athlon system.  One of the
> serial ports on this machine is connected to the serial console port
> on a second machine (my home firewall/bridge, running 4.2-STABLE).
> 
> The firewall's serial console speed is set to 115200.  The builtin
> serial ports on both machines are 16550A's.
> 
> I'm getting lots and lots of silo overflows on the Athlon when I
> generate a large amount of output from the firewall (e.g., if I do
> "ls -ls", the output is badly garbled, and I get kernel messages on
> the Athlon about silo overflows).
> 
> The Athlon's serial port (sio1) is using IRQ 3, and is =not= sharing
> this IRQ with any other hardware on the system.
> 
> I've tried patching isa/sio.c to set a lower receive FIFO threshold,
> but even with a threshold of FIFO_RX_MEDL, I still get silo overflows
> unless I reduce the console speed to 19200 or slower.
> 
> I'm really surprised that I should be getting silo overflows on an
> 800-MHz Athlon -- which, I would think, should have plenty of computing
> power available to handle serial interrupts without losing any input.
> 
> It works flawlessly, BTW, if I run Win98 on the Athlon and connect to
> the firewall via Hyperterm -- so I assume the problem is in the FreeBSD
> serial port driver, and not in my hardware.
> 
> I understand this "silo overflow" problem has been around for a long
> time, but I wanted to bring it up again to make sure it wouldn't be
> forgotten and would (hopefully) get fixed.
> 
> Rich Wales         richw@webcom.com         http://www.webcom.com/richw/
> 
> 
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--Roman Shterenzon, UNIX System Administrator and Consultant
[ Xpert UNIX Systems Ltd., Herzlia, Israel. Tel: +972-9-9522361 ]


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