From: jeh@cmkrnl.com
Newsgroups: misc.forsale.computers.d
Subject: Re: HELP: Monitor resolution
Date: 5 Jan 93 01:48:38 PST
Distribution: usa
Organization: Kernel Mode Consulting, San Diego, CA

In article <1i3alcINNls9@shelley.u.washington.edu>,
 topcat@hardy.u.washington.edu (Thanh - Vincent) writes:
> i have a hewlett packard video graphics color display but i no longer have
> the manuals to figure out how many ??.mm per dot or what is the highest
> resolution that this monitor can handle.  
> [...]
> my question is there a way for me to figure out how much resolution this
> monitor can handle?  

If your post had included the MODEL NUMBER of the monitor, you'd probably
have a definitive answer by now.  

> is there a program to do that?  

Ummmm, not really.  A program could be written which would step your video 
card through all the various resolutions of which it's capable and you could
look and see which ones work...

> since i have a 256k vga card now, the highest resolution that i
> can get is 640x400x256.  if i force it to something higher, i get a blank
> or one color screen.  

...and you've been doing some of that already.  But such a program would be
specific to your particular video card (or family of cards).  The monitor might
be able to handle modes which your video card can't generate, and you wouldn't
learn about them by this method. 

You said "640x400x256".  The last number is the no. of simultaneous colors. VGA
(and Super VGA) monitors don't care about that.  They do care about the
vertical sweep rate, which is usually something like 60 Hz, 70 Hz, etc.  A
monitor that works at (for example) 1024x768x60(Hz) won't necessarily work at
(for example) 024x768x70(Hz).  

> i read somewhere that you can damage the monitor if you force it into a 
> resolution that it cannot handle.  

This is true of some monitors.  However, given the way HP usually designs their
equipment, I'd be willing to make a small bet that there's nothing you can put
into its input connector (other than excess voltage :-) that would damage it. 

> oh, and what's the deal with those .24mm dot or .31mm dot mean anyway?

In a color monitor, the phosphors (the funny chemicals that actually emit the
light from the screen) are laid down in discrete dots or (in Trinitron-style
tubes) discrete vertical stripes.  ".24mm dot pitch" means that you have a
complete set of three dots or stripes (one red, one green, one blue) every .24
mm -- or about 4 per mm, or about 100 per inch.  

This places an upper limit on the "horizontal resolution" -- in a figure like
640x400, that's the "640" number. For example, if the monitor screen is sized
so that the display area is about seven inches wide, then at .24 mm dot pitch,
or about 100 dots per inch, 640 horizontal resolution, or maybe 800, is about
the most you'll be able to see. 

The monitor's sweep circuits might be able to handle (for example) 1024x768,
but you are not going to be able to see 1024 differently-colored pixels on each
horizontal scan line, because there just aren't that many differnt
light-emitting dots on the screen.  

Running the monitor with a horizontal resolution higher than its dot pitch
allows will not damage the monitor, but it won't let you see any more detail
than you would at the lower res. 

In a non-Trinitron monitor, the "dot pitch" also affects the maximum usable
vertical resolution.  

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
drivers, internals, networks, applications, and training for VMS and Windows-NT
uucp 'g' protocol guru and release coordinator, VMSnet (DECUS uucp) W.G., and 
Chair, Programming and Internals Working Group, U.S. DECUS VMS Systems SIG 
Internet:  jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
Uucp:  ...{crash,eisner,uunet}!cmkrnl!jeh