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From: jeh@dcs.simpact.com
Newsgroups: comp.os.vms,comp.sys.dec
Subject: Re: Parallel printers on a VAX
Message-ID: <1753.2721c4a9@dcs.simpact.com>
Date: 21 Oct 90 22:54:17 GMT
References: <680@incstar.uucp>
Organization: Simpact Associates, San Diego CA
Lines: 41

In article <680@incstar.uucp>, lhotka@incstar.uucp (Glamdring) writes:
> What is the best way to connect [parallel-interface] printers to our 6410 
> running VMS?  

Assuming your 6410 has a VAXBI bus (some 6400 configurations live quite happily
without one), you could get some DMB32's (three of them) to give you three
parallel ports along with 24 serial ports.  This would be hideously expensive 
($15K total) unless you need the 24 extra serial ports anyway. 

Although it would be possible to build a multiple parallel printer i/f for the 
VAXBI bus, no one has done so to my knowledge.  The minimum required complexity 
of a VAXBI option makes the price prohibitive.  

There are some general-purpose parallel I/O options for the VAXBI.  There is
DEC's DRB32, and ours (Simpact's) which is an exact emulation of two DR11W's.
However, no printer drivers that I know of will talk to these.  They're also
pretty expensive, as printer ports go.  

This leaves you with serial-to-parallel converters.  In my experience these
work well, and they're pretty inexpensive.  Black Box has several models in
their catalog.  Make sure you get one that matches your printer's electrical
interface (Centronics vs. Data Products) and physical connector, and make sure
it does xon/xoff flow control to the host.  Also, look out for printers that
have the Data Products "long lines" option.   

My personal advice is to get one withOUT a built-in buffer, or at least one
with a defeatable buffer, if at all possible.  The VAX print spooler system
does all the "buffering" necessary, and it is a minor annoyance to submit a
print job, look at the queue and find that the VAX thinks its done, only to go
to the printer perhaps half an hour later and find it out of paper.  You 
can't stop/abort a job that's in the buffer, either.  

Lantronix makes a LAT terminal server with a parallel printer port on it 
in addition to some number of serial ports.  This makes sense only if you need 
the extra serial ports anyway; otherwise, use existing serial ports with 
s-p converters.  

	--- Jamie Hanrahan, Simpact Associates, San Diego CA
Chair, VMSnet [DECUS uucp] and Internals Working Groups, DECUS VAX Systems SIG 
Internet:  jeh@dcs.simpact.com, or if that fails, jeh@crash.cts.com
Uucp:  ...{crash,scubed,decwrl}!simpact!jeh