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Date:      Fri, 1 Sep 2000 13:41:01 -0500
From:      "Jim King" <jim@jimking.net>
To:        "Gary Kline" <kline@thought.org>, "Warner Losh" <imp@village.org>
Cc:        <freebsd-stable@FreeBSD.ORG>
Subject:   Re: bad 16550A maybe? 
Message-ID:  <002d01c01444$350c8b00$a44b8486@jking>
References:  <200009010501.WAA54972@tao.thought.org>   <200009011832.MAA37168@harmony.village.org>

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> In message <200009010501.WAA54972@tao.thought.org> Gary Kline writes:
> :   This just showed up on my console (and dmesg) from my new 4.1 system:
> :   sio0: 1 more silo overflow (total 1)
> :   Could this be why moused is having trouble with recognizing my
> :   COM1 mouse?  Bad 16550A?
>
> Maybe.  silo overflows happen because the machine is too slow to
> service the interrupt before the buffer overflows (but unless it is a
> 386SX25 you should have enough CPU power).  It can also be caused by
> baud rate mismatches, but that's fairly rare and unusual (you usually
> get framing errors from a 16550A in this case).  This can also be
> caused by other hardware misbehaving and blocking interrupts.

I think we'd see a lot fewer of these messages on the mailing lists if sio.c
set the 16550A trigger level to 8 bytes instead of 14 bytes.  That's the
first thing I do when I see this problem, and that usually fixes it; much
easier than replacing the misbehaving hardware. :-)

Jim




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