agodwin@acorn.co.uk (Adrian Godwin) (11/05/90)
I'm trying to connect a Mitsubishu high-resolution monitor (32kHz, BNC inputs, no concessions at all to VGA standards, which it pre-dates) to the VGA port on a Compaq 386. It works fairly well, but only in monochrome. The Compaq's self-determining setup detects a Mono VGA monitor, and won't do colours. I've found some references to the possibility that the loading on the RGB signals are used to configure the monitor type, and the ID bits on the VGA connector (pins 11, 12, possibly pin 4) are ignored. Does anyone know for sure what the rules are ? What about SVGA - is that monitor capability sensed automatically too ? Thanks in advance, -adrian
Nandu@cup.portal.com (Narendra J Kulkarni) (11/06/90)
Most of the clone VGA cards ignore the moniter ID bits, they sense moniter type, mono/color/or no moniter by load on the RGB lines, the RAMDAC output of the VGA DAC is a current output, usually the VGA card has a 75 ohm ter minating resistance and the moniter has 75 ohm on RGB lines, the VGA card senses the voltage developed on the RGB lines by means of a comparator and detects the moniter, for mono moniter only one line usually green has 75 ohm for color all three have 75 ohm, your problem may be that the moniter does no t have terminating resistor, or something is not hooked right, make sure that your RGB return lines are connected to RGB return on VGA 15 pin connector
commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) (11/07/90)
agodwin@acorn.co.uk (Adrian Godwin) writes: >I'm trying to connect a Mitsubishu high-resolution monitor (32kHz, >BNC inputs, no concessions at all to VGA standards, which it pre- >dates) to the VGA port on a Compaq 386. >It works fairly well, but only in monochrome. The Compaq's self- >determining setup detects a Mono VGA monitor, and won't do colours. >I've found some references to the possibility that the loading on the >RGB signals are used to configure the monitor type, and the ID bits >on the VGA connector (pins 11, 12, possibly pin 4) are ignored. >Does anyone know for sure what the rules are ? >What about SVGA - is that monitor capability sensed automatically too ? I don't know how Compaq does it, but here is the connector pinout of an IBM color VGA connector (model 8513): You might try various combinations of open and ground on pins 11 and 12. 1 Red video 9 Reserved 2 Green video 10 Ground 3 Blue video 11 Monitor sense (ground) 4 Reserved 12 Monitor sense (open) 5 Self test 13 Horizontal synch 6 Red video return (coax shield) 14 Vertical synch 7 Green " " " " 15 Reserved 8 Blue " " " " On IBM monitors, the "self test" line causes a white raster on the screen when the cable is disconnected. The video signals are terminated at 75 ohms. -- Frank Reid reid@ucs.indiana.edu