The reason is that the SUN 19" monitor GDM-1962 (and also the SUN 16" monitor GDM-1662) only synchronize on the COMPLETE FIXED FREQUENCY combinations:
Hor.= 61.8 kHz with Vert.= 66 Hz and also on:
Hor.= 71.7 kHz with Vert.= 76 Hz.

Hor. freq. = line frequency, Vert. freq. is Frame refresh rate and
Hor. freq. = Vert. freq. x number-of-lines.
Vert. resolution = number-of-lines (minus a few invisible lines)
So the only Vert. resolution (number-of-lines) that you can get with these monitors is about 936 or 943 .

To get such fixed frequency combinations, you need special a video board that allows to program the Hor. and Vert. frequencies exactly.
Such video boards are marketed by specialized companies like MIRAGE in the USA or THRUPUT Direct in Bristol, England. (See the E-mail from Tony).

The 20" SUN Premium (or SONY) GDM-20D10 is not a complete fixed-frequency monitor,
but a MULTISYNC MONITOR that synchronyzes only in the high-frequency range:
Hor. 61.8 kHz to 81.1 kHz ,with
Vert. 66 Hz to 76 Hz Hz
That is why the 20" SUN Premium (or SONY) GDM-20D10 synchronzes at most PC video settings that include Vert. freq.= 75 Hz and resolutions 1024x768, 1152x864, 1280x1024
See: SUN 20" Premium (or SONY) GDM-20D10 monitor to a PC with Windows 95 or 98

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Return-Path: tonyf@mcsltd.co.uk
Reply-To: tonyf@mcsltd.co.uk
From: "tony" tonyf@mcsltd.co.uk
Subject: Using Fixed Frequency Workstation Monitors on PC's
Date: Mon, 3 Aug 1998 13:39:18 +0100
X-MSMail-Priority: Normal

Go to the site
http://www.mirage-mmc.com in USA, or
http://www.ultraspec.com/1395.htm in Bristol, England,
as they market a range of graphics cards which operate with fixed frequency monitors.
European distribution is by a company called THRUPUT Direct in Bristol, England.

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Best, The Netherlands, 24 July 1998.
last update: 15 March 1999.