Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hpvcfs1!neff
From: neff@hpvcfs1.HP.COM (Dave Neff)
Newsgroups: comp.sys.mac
Subject: Re: HP DeskWriter Performance on a Plus
Message-ID: <780057@hpvcfs1.HP.COM>
Date: 25 Sep 89 18:47:31 GMT
References: <22051@cup.portal.com>
Organization: Hewlett Packard, Vancouver, WA
Lines: 46

> Thanks to HP for illuminating some of the reasons the DeskWriter is
> so swift.  I was frankly quite disappointing by the marketing hype
> surrounding the DeskJet vs. DeskJet Plus, because it talked about
> speed advantages "in certain cases" but really didn't address "average"
> documents, nor spell out what cases had been optimized. I ended up
> having these two models side by side, running what I felt were "typical"
> usages, and the Plus showed around a 5% advantage (perhaps stop watch
> error?).

The DeskJet+ is mainly faster when the centronics port is used and when
dealing with graphics output (compressed or otherwise) and font downloads.
If you are using a serial port and/or printing mainly text the DeskJet+
will not be much faster.  Most of the third party DeskJet drivers for the
Mac are CPU and/or IO limitted so the DeskJet+ does not give much of
a speed advantage.  The DeskJet+ also picks and moves paper twice as
fast but the ink cartridge still moves at the same speed.  This makes the
printer seem much faster (watching a DeskJet load paper after using a
DeskJet+ is painful) but the paper pick/move time is really a small part
of the overall print time (that was maybe the 5% you saw).  For centronics
graphics only output the DeskJet+ is really 5 times faster than a DeskJet.
For text its a bit faster.  Depending on your mix of text to graphics,
what IO is being used, and how fast your CPU can generate the images,
the numbers can be anywhere between no faster to 5 times faster
comparing a DeskJet to DeskJet+.  If you are using a serial port at
19.2K baud and your application/driver uses the mode 2 compression for
full page graphics, and can generate the images fast enough, the DeskJet+
will be about 2 to 3 times faster than a DeskJet.  Obviously it is
impossible to say the DeskJet+ is N times faster than a DeskJet when
there are so many variables that affect the result (CPU, graphics, text,
downloads, compression modes, and IO).  Comparing the DeskWriter to the
other Mac printers is easier since the main variable is CPU and memory
configuration.  Everything else is pretty much fixed.

> Could we learn more about when Mode 3 compression is a winner? Does it help
> with documents that are typical of rich output from Word, Draw or Paint?

I don't know to what extent we are allowed to talk about mode 3 compression.
We have applied for a patent on the technique so it has been made public
to the extent that the patent application requires.  It basically helps
with everything except heavily dithered scanned images.  It is similar
to compression modes used by FAX machines but enhanced.  It has been
added to the official HP Printer Control Language specification.  I'll
try to find out if we can talk about more details.

Dave Neff
neff@hpvcfs1.HP.COM