Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!sgi!daisy!cplai
From: cplai@daisy.UUCP (Chung-Pang Lai)
Newsgroups: comp.lang.postscript
Subject: Re: Why is Display Postscript Fast when Printer Postscript is Slow?
Message-ID: <2164@daisy.UUCP>
Date: 16 Dec 88 07:13:18 GMT
References: <1481@helios.ee.lbl.gov>
Reply-To: cplai@daisy.UUCP (Chung-Pang Lai)
Organization: Daisy Systems Corp., Mountain View, Ca.
Lines: 42

In article <1481@helios.ee.lbl.gov> forrest@ux1.lbl.gov (Jon Forrest) writes:
]I'd like to hear comments about how Display Postscript is fast
]enough to be used as a display system whereas Printer Postscript
]seems to be the bottleneck on many laser printers. 
]What are the other differences that make the speed of
]Display Postscript so much better?
]
]Jon Forrest		Lawrence Berkeley Lab., 486-4991
]forrest@lbl.gov			(internet)
]ucbvax!lbl-csam!ux1!forrest	(uucp)
]FORREST@LBL			(bitnet)

People in Adobe should answer this, but I can contribute what I heard.
I actually asked the same question when I took a PostScript programming
course at Adobe Systems.  Back then, Display PS is not out yet, they
showed us a demo video tape and claimed that they did not speed up
the video. :-)  I doubted the tape back then because a page that used to
take 10 minutes on a LaserWriter flashes on the screen in 10 sec.
Of course, I believe them now after seeing the real demo in conferences.
The instructor did not answer my question directly but instead just
said that they will use the Display PS technology in future release of PS 
controller for printers.  I guess they wanted to keep it as a trade secret.

These I heard from other sources:
1. 72 dpi vs 300+ dpi is a big difference.
2. Display PS cheats when handling small size font.  They use bitmap
   font when you can't tell the difference.
3. They pass pre-scanned tokens instead of sending streams of ASCII 
   postscript code.
I heard the above, don't blame me for any mistake.

I am taking a NeWS programming class this week at Sun.  Doing PostScript
interactively is really fun compared to waiting at a printer.  PostScript
is only a small part of NeWS.  Sending a PostScript picture to my fellow
classmate's screen is fun.  It is like crossing X-window with PostScript
and Object Oriented Programming but not quite.


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{cbosgd,fortune,hplabs,seismo!ihnp4,ucbvax!hpda}!nsc!daisy!cplai    C.P. Lai
Daisy Systems Corp, 700B Middlefield Road, Mtn View CA 94039.  (415)960-6961