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From: mills@ccu.umanitoba.ca (Gary Mills)
Newsgroups: comp.unix.wizards
Subject: Synchronous Device Driver for SunOS
Message-ID: <1991Jun11.030213.21943@ccu.umanitoba.ca>
Date: 11 Jun 91 03:02:13 GMT
Organization: University of Manitoba, Winnipeg, Canada
Lines: 18

Is c.u.w the right place to ask about device drivers?  Is there a better place?

I have a bisync driver running on a Sun-4/280 that works correctly most of
the time, but under certain conditions, the remote host reports transmission
errors.  These occur, for example, when the Sun is heavily loaded with disk
i/o, when it's writing a lot of console log messages, or when I raise the
bit rate from 9600 to 19.2 kb.  I believe the errors are caused by transmitter
underrun in the Z8530 serial device.  This implies that the cpu is not able
to respond quickly enough to the transmitter interrupt.

Does anyone know of any tricks to avoid this problem?  I would like to be
able to run it at 19.2 kb.  The bottom half of the driver merely moves a byte
from a buffer to the device at each transmitter interrupt, so that part can't
be too slow.  Am I up against a limit here?  The receiver seems to handle
the speed with no problem, but it has a 3-byte FIFO.

-- 
-Gary Mills-         -Networking Group-          -U of M Computer Services-