Path: utzoo!utgpu!watmath!att!rutgers!ucsd!usc!apple!sun-barr!newstop!sun!imagen!qmsseq!pipkins
From: pipkins@qmsseq.imagen.com (Jeff Pipkins)
Newsgroups: comp.periphs
Subject: Re: How fast can a typical Laser printer Centronix Interface go?
Keywords: Laserprinter, centronix, speed
Message-ID: <48@qmsseq.imagen.com>
Date: 16 Nov 89 23:37:22 GMT
References: <218@cmic.UUCP>
Reply-To: pipkins@qmsseq.UUCP (Jeff Pipkins)
Organization: QMS Inc., Mobile, Alabama
Lines: 24

In article <218@cmic.UUCP> garvey@cmic.UUCP (Joe Garvey) writes:
>I was told by a vendor that the Centronix interface in a typical (Laserjet II)
>interface would only transfer data at about 50 Kbaud (yes I know it's byte
>wide, but it's easier to compare to a serial interface this way).

Using a typical PC (what does this mean anymore?) running DOS, the 
Centronics interface is software bound.  You can expect to get a maximum
of about 1K bytes/sec (equivalent to a 9600 baud serial connection).
A program that drives the port directly (*NOT* reccommended) can reach
speeds that violate the Centronics timing specs.  I wrote a replacement
DOS printer driver to speed things up.  If you use "copy /b file lpt1"
(/b is important), it will drive just about any printer at close to its
rated transfer speeds.  We've seen bursts of 30K bytes/sec to a PostScript
printer and speeds in excees of 90K to a dummy card with a scope
attached to it, when using a modest 286 machine.

If there is enough interest, I'll ask the boss if I can release the
driver.

P.S. The /b option of the copy command is equivalent to using MS-DOS
function 44h to set the "raw" (uncooked) mode on a character device.

Also: You can probably reach speeds of 10K bytes/sec by using the
BIOS int 17h function call to print instead of going through DOS.