Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hpvcfs1!neff
From: neff@hpvcfs1.HP.COM (Dave Neff)
Newsgroups: comp.sys.mac
Subject: Re: A few Deskjet+ observations
Message-ID: <780003@hpvcfs1.HP.COM>
Date: 9 May 89 19:10:40 GMT
References: <10452@orstcs.CS.ORST.EDU>
Organization: Hewlett Packard, Vancouver, WA
Lines: 44

>definite alternative to the Imagewriter.  I haven't used a Deskjet but 
>if, as some people have suggested in this group, there is no improvement 
>in speed between the Deskjet and the Deskjet+ when run from a mac, then 
>for approximately $210 dollars more you can get a printer that is 2 to 3 
>times faster than an Imagewriter.

This statement surprises me.  The DeskJet is not IO limitted at 19.2K baud
but the DeskJet+ is IO limitted.  In fact, on a DeskJet using 9600 and
19.2K baud makes little difference but on a DeskJet+ this makes a big
difference (2X).  If your DeskJet driver uses our data compaction modes a page
of 300DPI graphics will typically be about 200K (sometimes more, sometimes
less).  At 19.2 K baud this is about 2K per seconds so it should take
100 seconds to print on a DeskJet+.  If your driver really building
a page fast enough and using the data compression modes a DeskJet+
at 19.2 K baud should be about twice as fast as a DeskJet.  I see
a couple of possibilities:

1) Is you printer driver optimized for the DeskJet/DeskJet+?  This
means does it use data compression (mode 2)?  There are some
pseudo data compression tricks that are often done for the LaserJet
printer that makes the DeskJet SLOWER.  This mainly involves compressing
data by continually changing margins.  This achieves performance
improvement on a LaserJet but performance degredation on a DeskJet/DeskJet+.

2) Are you printing some sort of page that does not compress well (like
a scanned image)?  Like I said, mode 2 compression generally results
in a 200K file versus the 1000K file of uncompressed graphics.  If it
really took 7 minutes to print a page at 19.2 K baud it sure sounds
like the data is uncompressed or does not compress well.

3) You are using 19.2 K baud aren't you?  This is not the default
BAUD rate of a DeskJet or DeskJet+.

The DeskJet is about the same speed in printing simple text as
the DeskJet+ but when it comes to graphics the DeskJet+ is much
better.  Maximum graphics performance of course requires a parallel
port on a DeskJet+.  On a DeskJet parallel versus serial at 9600 or
19.2 K baud made little difference when printing graphics.  For 
a DeskJet+ parallel performance is 5X a DeskJet for 300 DPI graphics.
Mac users might want to try a 57K baud to parallel conversion box when
printing to a DeskJet+.

Dave Neff
hplabs!hpvcfs1!neff