Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!lll-winken!elroy.jpl.nasa.gov!ncar!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.arch
Subject: hi-res monitors
Summary: they exist, but...
Message-ID: <1990Nov15.002819.14763@ico.isc.com>
Date: 15 Nov 90 00:28:19 GMT
References: <3300214@m.cs.uiuc.edu>
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 50

gillies@m.cs.uiuc.edu writes:

> Why don't we see monitors that are 2048*1532, at 150 dpi?  Would the
> radiation from the high-frequency modulators fry your brains?

There are some monitors with 150 dpi resolution.  Princeton has had one for
a year or more; Cornerstone (which makes the controller for that Princeton
monitor) has had a large-screen 120 dpi for a while and I think now has a
large-screen 150 dpi.  They're not cheap...and part of the reason is the
frequencies at which they have to operate.  (It's unwieldy to connect the
monitor to the machine with a waveguide.:-)  

There are three factors which make high-res monitors tough:
	- Video memory requirements and bandwidth requirements go as the
	  square of the increase in resolution.
	- You can't get away with the interlace cheat, because you just
	  can't make the sweep circuitry stable enough to keep the two
	  fields spaced accurately.
	- You need a good refresh rate--the sort of scrutiny that a high-
	  res monitor gets will make any flicker unacceptable.  It's got to
	  be > 60 Hz; it's better at around 70.
By the time you factor all these together (and allow for retrace times,
which have to be generous), a 1600x1280 display is up around 200 MHz, and
the 2048x1532 in ">" is pushing 300 MHz.  It can be done (and has been) but
it's not cheap enough to approach the knee in the price:quantity curve.

Also, note that the quadratic effect of increased resolution can get you on
the CPU side...you have to move a lot of bits.  (Today, though, the limit
is likely to show up in the video-memory subsystem first--it's so busy
shoveling bits to the screen that the CPU ends up waiting.)

> Is there a problem with the physics of monitor phosphors?

Not really...assuming you're talking about monochrome.  Forget color for
the time being...it's not going to do any good to be at 150 dpi (which is
roughly 6 dots/mm) with a .25 mm dot pitch tube!

That, unfortunately, points to another problem in pricing these beasts:
"Everyone" wants color so that they can have their cute window borders and
clocks with multi-color hands, and other display-on-bad-drugs useless
effects (but that's another flame for another time:-)...
As a result, people are buying cruddy-looking color displays, driving the
prices down, and ignoring the good-looking mono displays, which keeps the
mono quantities down and prices up.  NeXT is a prime example here--they
have one of the best-looking (most readable and honestly *useful*) B&W
displays I've seen, but they've been pushed into color by the feature-mad
marketplace.
-- 
Dick Dunn     rcd@ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   Cellular phones: more deadly than marijuana.