Path: utzoo!attcan!uunet!bu.edu!snorkelwacker!tut.cis.ohio-state.edu!rutgers!cbmvax!grr
From: grr@cbmvax.commodore.com (George Robbins)
Newsgroups: comp.bugs.4bsd
Subject: Re: Problems with a dmf-device (BSD4.3)
Message-ID: <13144@cbmvax.commodore.com>
Date: 11 Jul 90 08:24:27 GMT
References: <522@bsiao.UUCP>
Reply-To: grr@cbmvax (George Robbins)
Organization: Commodore, West Chester, PA
Lines: 31

In article <522@bsiao.UUCP> tvdl@bsiao.UUCP (Timo van der Laan) writes:
> We have a VAX 11/750 running BSD4.3. Since we use a trailblazer (for news),
> the message "dmf0: silo overflow" gets printed rather often on the console.
> The trailblazer operates at 19.2 Kb and is the only active 'terminal'
> when the above message gets printed. 
> 	Question 1: Is this a serious error?
> 	Question 2: Is there a way to prevent it?

This isn't unusual - the dmf32 has a fairly small input buffer (silo) and the
750 probably can't keep up to incoming bursts.  On our 785 (Ultrix) we would
get these messages any time two uucp lines were active at 9600/19200 baud.

It's not serious as far as uucp is concerned, some incoming characters are
dropped but the protocol eventually recovers.  It is something of a problem
if you have activity on other lines on the DMF32, since other lines can also
lose input when the uucp line overflows the silo.

Some interfaces have larger silo's, but they all seem to be on the same order
of magnitude.  I switched to a Able DH11 emulator board, and the problem occured
much less frequently, but didn't go away.  Unfortunatly, the Ultrix DH11 driver
has some kind of bug that led to system crashes when it did overflow...

I'd suggest just ignoring the problem if you can, putting other serial lines
on a separate interface if you have difficulties.  You may also want to try
running the Trailblazer at 9600 baud - in many cases you'll only lose 20-30%
of the thruput, but also limit input burst rates.

-- 
George Robbins - now working for,     uucp:   {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing:   domain: grr@cbmvax.commodore.com
Commodore, Engineering Department     phone:  215-431-9349 (only by moonlite)