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From: tjr@cbnewsc.att.com (thomas.j.roberts)
Newsgroups: comp.sys.ibm.pc.hardware,comp.sys.ibm.pc.misc
Subject: Tired Eyes - Flickering VGA - Solution!
Message-ID: <1991Mar17.224308.17946@cbnewsc.att.com>
Date: 17 Mar 91 22:43:08 GMT
Followup-To: poster
Distribution: na
Organization: AT&T Bell Laboratories
Lines: 33

I have noticed that my eyes were tired A LOT more often lately, and had
attributed it to merely getting older. I believe I have found a direct
cause - the flicker on my VGA monitor. Many (most ?) people do not see
any flicker on a standard VGA monitor refreshed at 60 Hz (vertical sync
rate); I notice it, but had felt that I could live with it - it wasn't
really very noticeable.

	I see the flicker as an intensity variation of the overall
	screen - it is most noticeable when the screen has a large
	white background or when I see the screen out of the side
	corner or bottom of my eye's field of view. Windows is unuseable
	for me, unless I change all background colors to black.
	I estimate that the flicker I see from a 60 Hz non-interlaced
	screen is about 10 Hz - it is clearly nowhere near 60 Hz -
	I assume that there is some complicated sort of aliasing going on.

This is not a new observation - just a realization on my part that I
am affected. Note that Eurpoean ergonomic standards require a refresh
rate > 70 Hz (I don't know the exact requirement, but 60 Hz is definitely
not allowed).

My solution - I purchased a Gateway-2000 PC with a Diamond SpeedStar
SVGA card (uses the Tseng Labs ET4000AX chip); I upgraded to a Sony 1304
Monitor. This combination will use a vertical scan rate of 72 Hz
(non-interlaced) in VGA and 800x600 modes; it will also use 60 Hz
interlaced for 1024x768 (which has a noticeable flicker for me). I can
now run Windows without any visible flicker, and have used the system for
> 4 hours in one sitting without problems. This is not the only SVGA
card that can use 72 Hz modes, but this is the most affordable monitor
I have been able to find that can - especially in 800x600. It looks Great!

Tom Roberts
att!ihlpl!tjrob  TJROB@IHLPL.ATT.COM