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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!mtuxo!mtune!akguc!codas!bsdpkh!latham
From: latham@bsdpkh.UUCP (Ken Latham)
Newsgroups: net.micro,net.micro.pc
Subject: Sigma Multi-Mode Graphics Board
Message-ID: <208@bsdpkh.UUCP>
Date: Wed, 18-Jun-86 16:54:24 EDT
Article-I.D.: bsdpkh.208
Posted: Wed Jun 18 16:54:24 1986
Date-Received: Fri, 20-Jun-86 02:01:08 EDT
Reply-To: latham@bsdpkh.UUCP (Ken Latham)
Organization: AT&T-IS (SDSS), Orlando Fl.
Lines: 42
Keywords: EGA, Horizontal Sync
Xref: watmath net.micro:14847 net.micro.pc:8726


Not being a hardware nut, nor knowing much about the physics and electronics
of video, I was hoping some one could give me some pointers or help with a
problem I have.

I recently obtained a Sigma EGA board (w/ CGA, Monochrome, short card) and
am wondering if I should risk trying to hook the thing up to my amdek710
monitor (16.4 KHz horz. sync) in EGA mode.

I know this seems like a no-no as the EGA standard requires a higher sync
rate.  However, the Sigma board does work in an extended (640x200 w/ 16 colors)
mode on the AMDEK710.

The reason I think the board might work is that the oscilator on the board
is marked "16.4 KHz". Another Sigma board I have requires ~24 Khz (Sigma 400)
and I have a matching monitor at 24 Khz.  The Sigma400 contains an oscilator
on the board marked "24.1 KHz".

Q. Am I dreaming or doesn't the oscilator on the card limit it to a maximum
   Horizontal synchronization frequency?
   i.e.
   Can the output signal exceed this frequency(16.4 KHz)?

Q. Is the incompatability due not to horizontal sync. frequency but due to
   extra video control signals which my amdek does not understand?


I hate to "hook it up and see" because the board and monitor both give
such explicit warnings of damage if you mismatch their abilities!


			Ken Latham, AT&T-IS (via AGS Inc.), Orlando , FL

			uucp: ihnp4!bsdpkh!latham

P.S.  The documentation also states that I need a 
      ROM NEWER THAN "1/27/82" (I think)  Mine is dated "1/27/82"
	
	What is the difference they require? It seems to work ok!


THANKS In Advance!!!!!