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From: mackay@CS.WASHINGTON.EDU (Pierre MacKay)
Newsgroups: comp.laser-printers
Subject: Flow Control Problems
Message-ID: <9001051617.AA07885@crayola.cs.UMD.EDU>
Date: 5 Jan 90 01:01:59 GMT
References: <8912262207.AA05813@crayola.cs.UMD.EDU>
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Approved: laser-lovers@brillig.umd.edu

I have been working on an application which runs the zs1 serial port on 
a 3/60 with SunOS4 at the physical limit of 960 characters/second
continuously for twenty or thirty minutes.  Using the ``Posix''
non-canonical interface with the port I have had no problem 
(Sun does not yet claim POSIX compliance, but they do a darned good
job in most places where it counts.)  

I have been especially satisfied with the performance of the 3/60,
since I have had troubles with every other system I have tried to port
the application to, including the Sparcstation.  On the 3/60 it runs
perfectly, but it should be recognized that this application reads
without any requirement for handshaking.


Your problem probably relates to the need for handshaking, as the
laserwriter comes back looking for more data.  I believe that
the printcap can introduce various forms of delay and padding which
might solve the problem.  I seem to remember that the recommended
Sun printcap involves rows and rows of padding characters.

Otherwise, try SunOS4.  It is good stuff.

Pierre MacKay