Path: utzoo!attcan!uunet!mailrus!iuvax!cica!tut.cis.ohio-state.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!sunybcs!rutgers!cbmvax!peter
From: peter@cbmvax.commodore.com (Peter Cherna)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Video Signals
Keywords: RGB, digital, clock signals
Message-ID: <9763@cbmvax.commodore.com>
Date: 21 Feb 90 17:35:03 GMT
References: <9?!#+`-@rpi.edu> <9726@cbmvax.commodore.com> <2269@ultb.isc.rit.edu>
Reply-To: peter@cbmvax.cbm.commodore.com (Peter Cherna)
Organization: Commodore, West Chester, PA
Lines: 47

In article <2269@ultb.isc.rit.edu> dcr3567@ultb.isc.rit.edu (D.C. Richardson )
writes:
>What, exactly, *IS* Hedley Hires?

Hedley Hires is a pair of graphics modes that yield 1008 by 800 (NTSC) or
by 1024 (PAL) in two or four shades of gray, using special hardware and
software.

These modes are often used by people in the desktop-publishing business.

The Moniterm Viking One monitor for the Amiga (list of $1995 last time I
checked) is a 19" black-and-white monitor with a card for an A2000-class
video-slot containing the circuitry needed to achieve this display, and
a "JumpStart" disk containing a few system libraries updated to support
this mode.

The A2024 Monitor from Commodore is similar, but is only 14" in diagonal.
As well, the hardware is contained in the monitor, so it can be connected
to A500's or A1000's as well.  This monitor has been shown, but is not
generally available.

The Amiga actually outputs four or six different panels of the total display
area (depending on which mode), so a regular monitor will display a constantly
changing mess.  The Hedley-hires circuitry stores each panel in the right
place in a frame-buffer so that the display is correct on the Hedley monitor.
The side-effect of this is that there is a data-refresh rate of 10Hz or 15Hz.
(Of course, the monitor has a screen-refresh rate of (I believe) 70Hz, so
it's flicker-free.)  A few clever tricks in software allow for optimized
data refresh to smooth out mouse movement and such.

As a bonus, the Hedley circuitry allows the display of the regular modes
(320 or 640 horizontal by 200 or 400 vertical (256 or 512 in PAL))
in a crisp de-interlaced display, with dithered patterns to give a nice
gray-scale appearance.
 
Note that Moniterm makes large monitors for other systems, which may or
may not be similar, but you need the included video card and software to
get anything from your Amiga.

>Daniel Richardson
>Up Near The Great White North

     Peter
---
     Peter Cherna, Software Engineer, Commodore-Amiga, Inc.
     {uunet|rutgers}!cbmvax!peter    peter@cbmvax.cbm.commodore.com
My opinions do not necessarily represent the opinions of my employer.