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From: harkins@casbah.acns.nwu.edu (Don Harkins)
Newsgroups: comp.periphs.printers
Subject: Re: Re: How fast is a parallel port?
Message-ID: <1991Mar3.074920.7760@casbah.acns.nwu.edu>
Date: 3 Mar 91 07:49:20 GMT
References: <1991Feb28.125919.10505@sceard.Sceard.COM> <8400007@hpfcso.FC.HP.COM>
Organization: Northwestern University
Lines: 32


>> re: > It is possible to achieve far greater speeds by using faster gate and
>>     > buffer ICs.  In fact, the parallel port on the Hewlett Packard
>>     > HP9000/400T workstation is rated at 300 kilobytes per second.

> Vendors also play fast and loose with the "spec" (which is pretty vague in
> the first place).  Tektronix runs the "Centronics" interface on their 4693DX
> at a megabyte/sec.
>
> Regards,                                              Hewlett-Packard
> Bob Niland      Internet: rjn@FC.HP.COM               3404 East Harmony Road
>                 UUCP: [hplabs|hpfcse]!hpfcrjn!rjn     Ft Collins CO 80525-959


The Tektronix 4693DX manual specifies a 700KB / second rate in a data burst
using an extended definition of the Centronics protocol called TPI (Tektronix
Parallel Interface).  I heard from a Tek rep that a Metheus Display
controller was the only device Tek knew about that could out-run the 4693DX.
I tried a 286 10Mhz PC and could only do 12KB / second using int17 commands!
On the same PC, using my own assembly language routines like the ones 
described previously, I was able to get 70KB / second.

I suspect Tek made the 4693DX this fast so that they could use their
terminals to offload color data quickly.  Remember color needs rates 24x
faster to keep up with a monochrome printer (1 bit vs. 24 bits per pixel).

As far as your message Bob, this newsgroup is not the place for one printer
manufacturer (HP) to put down another.  It dosen't reflect well on you or
your company.

Internet:  harkins@casbah.acns.nwu.edu
           Don Harkins, Northwestern University