Path: utzoo!attcan!uunet!cpqhou!scotts
From: scotts@cpqhou.UUCP (Scott Shaffer @ Compaq Computer Corp.)
Newsgroups: comp.sys.ibm.pc
Subject: Re: connector on vga boards
Message-ID: <581@cpqhou.UUCP>
Date: 15 Mar 90 06:00:00 GMT
References: <1990Mar12.231833.19363@aucs.uucp>
Organization: Compaq Computer Corp
Lines: 27

In article <1990Mar12.231833.19363@aucs.uucp>, 870646c@aucs.uucp (Barry Comer) writes:
> 
> This may be a stupid queston, but I am going to ask it anyways. What is that
> little connector on most VGA boards for? Just wondering.

This interesting little connection (the one that is similar to a floppy
drive connector, btw, don't hook your floppy to it :) ), is called the
VGA Special Feature's connector.  It works like this:
Video data is processed exactly as normal, except, as the signal is
being sent to the VGA's internal Digital/Analog Converter (DAC), it is
also routed to this connector (hence the only signals there are the
Red, Green, and Blue guns, the Horiz. and Vert. sync, and a ground).
This feature is used by a number of the secondary enhanced-mode video
boards (such as Compaq's AG1024, Dell's TI thingy, and a couple of
others (Western Digital I think)).  This enables these manufacturers
to create boards that are entirely devoted to their enhanced modes (ie.
they don't have to emulate VGA).  They don't have to try to be register
or BIOS compatible on the VGA modes because the get that signal directly
from the VGA and just pass it through to their own DAC, and out to the
monitor.  Some VGA cards do NOT have this feature connector (to save
$$$), and thus they will not be compatible to these enchanced secondary
adaptors.  IBMs 8514 system is similar to these other enhanced-mode
adaptors, except that it ONLY works with MCA machines and gets the
video info off of the bus (I guess, where else?).  Thus, you can't
use 8514 in ISA machines.

* Scott Shaffer @ Compaq Computer Corp @ Houston, TX			*