SIO buffer overflows

Kent Stewart kstewart at
Thu May 29 08:23:11 PDT 2003

On Thursday 22 May 2003 08:08 am, Fergus Cameron wrote:
> i've been running BSD as a gateway on my old i486
> for a few years now and have just reconnected my
> modem (was on DSL).  unfortunately there
> is a constant problem with sio buffer overflows.
> not surprising i hear you say as it's in the bugs
> section of sio(4).
> still, the system is running 5.0 release well and
> i'm reluctant to decomission it over something
> trivial.  anyone ideas on how to tune to eliminate
> the overflows?  failing that what version would i
> need to drop back to 4, 3?  i don't remember the
> problem existing in late 4 (4.6-4.7) but cannot
> verify 100% at the moment.
> i've attached the dmesg output including errors
> from sio1 at 57600.  the test was a simple -- tip to
> the modem and then ati4 to generate enough output
> for the overflow.

They used to make I/O cards for the like of 486's that had fully functional 
16-byte FIFO's. I have some around but couldn't find them. When you turn on 
hardware controll, most of the errors go away. At least, this is the old 

FWIW, I would worry about the improperly dismounted messages in dmesg more 
than the sio problem.


Kent Stewart
Richland, WA

More information about the freebsd-questions mailing list