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From: rjn@hpfcso.HP.COM (Bob Niland)
Newsgroups: comp.periphs
Subject: Re: How fast can a typical Laser printer Centronix Interface go?
Message-ID: <8390002@hpfcso.HP.COM>
Date: 15 Nov 89 18:15:52 GMT
Article-I.D.: hpfcso.8390002
References: <218@cmic.UUCP>
Organization: Hewlett-Packard, Fort Collins, CO, USA
Lines: 26

re: "I was told by a vendor that the Centronix interface in a typical
     (Laserjet II) interface would only transfer data at about 50 Kbaud"

> Is this true, if so is it really worth having a centronix interface in a
> printer?

Yes, if only because the serial interface can only hit about 19.2Kbaud.
Incidentally, both interfaces are always present.

As I understand it, the LJ's I/O performance is limited not by the
interface, but by the architecture.  The LJ was designed back when RAM was
expensive, so it does not have a full page-image buffer.  Each laser scan
line is fabricated in real-time from a tokenized (partially pre-processed)
representation of the input data stream.  The processor is an 8MHz MC68000.
This design is also why Error 21 sometimes occurs.

The print engine will hold-off the interface when the parsing and tokenizing
can't keep up with the inbound data.   This is what limits I/O rates.

Regards,                                              Hewlett-Packard
Bob Niland      rjn%hpfcrjn@hplabs.HP.COM             3404 East Harmony Road
                UUCP: [hplabs|hpfcse]!hpfcla!rjn      Ft Collins CO 80525-9599

This response does not represent the official position of, or statement by,
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