Path: utzoo!yunexus!stpl!yugas!julius
From: julius@yugas.UUCP (Julius OKLAMCAK)
Newsgroups: comp.sys.atari.st
Subject: Re: Laser Speed
Message-ID: <793@yugas.UUCP>
Date: 1 Sep 88 03:23:26 GMT
Article-I.D.: yugas.793
Reply-To: julius@yugas.UUCP (Julius Oklamcak, Atari Canada)
Organization: C.R.E.S.S., York University, North York, Ontario, Canada, M3J 1P3.
Lines: 89

In article <1988@looking.UUCP> brad@looking.UUCP (Brad Templeton) writes:

>In article <3758@polya.Stanford.EDU> rokicki@polya.Stanford.EDU (Tomas G. Rokicki) writes:
>
>>PostScript engine is actually quite fast at rendering.  I say, if
>>the interpreter is your bottleneck, either you are plenty fast
>>(a minute a page or less) or your application is abusing PostScript.
>>.....
>>Maybe I'm spoiled.  But if I had a software package that took
>>ten minutes to print a single page, I'd return it.  And buy
>>something that works.
>>-tom
>
>I found this article quite funny.  The software I have always used
>has always printed nicely formatted text at around 6 pages per minute.
>(In this case, that is the speed of the LaserJet.)
>While I would certainly toss anything that took several minutes to print
>a page, I would also do that with anything that took a minute.  I find
>it incredible that people put up with this sort of thing.
>
>There's no reason you can't have nice typeset text as fast as the printer
>can output it.  The only reason is badly written software that was never
>tested properly for speed.  There's little excuse for that.
>
>I guess none of you are contemplating buying the Panasonic laser partner
>for the 11 pages per minute.  You wouldn't have anything to do with it.

Benchmarking laser printer speeds and 'through-put' speeds is a kettle of
fish.  Worse than attempting to benchmark systems and processors.  :-)

I recently did some simplistic timings to start to get a handle on things.
I created a document in Timeworks Desktop Publisher and printed it on three
lasers and one ink jet.  The results are interesting to say the least...  :-)

Atari SLM804      1.33           The results are in minutes.seconds.  The
NEC LC-890        5.54           LC-890 was running PostScript, the Roland
Roland LP 1100   14.52           is the same as the Panasonic, all output
HP DeskJet       20.44           was done via GDOS and appropriate drivers.

So.  What does this tell us?  (Besides that the SLM804 is the fastest :-)

First we need to take a look at how things work under the hood and at exactly
what is going on.  When TWDTP (Timeworks Desktop Publisher) prints, it opens
up a virtual printer workstation, executes the necessary commands to 'draw'
the page, and then gives a 'print the page' command.

During this time, depending on the device driver used, several different
things could be happening:

 The SLM804 driver simply allocates a bit-map the size of a page, draws to
 it, then sends it to the printer at approx. 3 mega-bits-per second.  If
 the other drivers worked this way, then we see why the SLM804 is faster.
 The maximum speed that you can send data down a parallel port is 2000-3000
 bytes a second.  A full page bit-map is approximately 990,000 bytes - but
 that is still only about 5  minutes (it appears that there must be an
 inefficiency somewhere in here when it comes to output devices with
 HP LJ emulation :-)

 The GDOS PostScript driver simply translates VDI calls to PostScript
 code and sends it down the serial port.

The major bottle-neck in printing and through-put speeds is getting the
data, a representation of the data, to the printer fast enough.  Ventura
will generate over 150k of PostScript code for a semi-interesting page with
two line art graphics and some text (do a print to disk on the VPSCOOP
document to see what I mean).  The laser then must interpret this PostScript
program and render an image into, guess what, a 990,000 byte bit-image of a
page.  As a result of this, some (most!) laser printers are more powerful
computers than the machines they are hooked up to.

Printing a page of raw text, especially listings and letters, is a snap for
a laser printer.  It dosen't have to do any real work.  Simply blit the
font image data to the page buffer, or even do it on the fly (as some of
these lasers with less than 1 meg do).  Tricks can also be used to do some
bit image graphics with a laser with around 512k of RAM.  Some software,
like Ventura, uses these and other tricks to get acceptable looking output
and printing speeds on HP LaserJet's and compatibles.

My next step in benchmarking lasers will be to create the same page that
was originally done with TWDTP under Ventura, and possibly a few of the
other packages that out there in the PeeCee/MessyDOS & Mac worlds, and
time the printings.

Julius Oklamcak                                         CIS: 70007,1070
Atari (Canada) Corp.                                    BIX: joklamcak
(416) 479-1266                                        GEnie: J.OKLAMCAK

	"I don't know what he is talking about.
		Do you know what he is talking about?" - Rambling Man