Hardware Reference
In-Depth Information
played. Of the vertical and horizontal frequencies, for CRT displays the vertical refresh
rateismoreimportantbecauseitcontrolsflicker.ArefreshratethatistoolowcausesCRT
screenstoflicker,contributingtoeyestrain.ThehighertherefreshrateyouusewithaCRT
display, the less eyestrain and discomfort you will experience while staring at the screen.
A
flicker-free refresh rate
is a refresh rate high enough to prevent you from seeing flicker
on a CRT. The flicker-free refresh rate varies with the size and resolution of the monitor
setting (largerandhigherresolutions requirehigherrefreshrates)aswellastheindividual
because some people are more sensitive to it than others. In my experience, a 75Hz re-
fresh rate is the minimum anybody should use with a CRT, especially at resolutions of
1024×768andhigher.Lowerratesproduceanoticeableflicker,whichcancauseeyestrain,
fatigue, and headaches. However, although a 75Hz vertical refresh rate is sufficient for
most, some people require a setting as high as 85Hz before the image is truly flicker-free.
For that reason, 85Hz is considered by VESA to be the optimum refresh rate for CRT dis-
plays. Because a refresh rate that is too high can reduce video performance by making the
adapter work harder to update the image more frequently, I recommend using the lowest
refresh rate you are comfortable with.
Note
CRTmanufacturers often usedthe term
optimal resolution
torefer tothe highest resolution a
given CRT monitor supports at the 85Hz VESA standard for flicker-free viewing.
Table 12.18
shows the correlation between resolution and refresh rates. As the resolution
and vertical refresh rate increase, so must the horizontal frequency. The maximum hori-
zontal frequency supported by the display is the limiting factor when selecting higher re-
fresh rates at a given resolution.
Table 12.18 Refresh Rates Comparison
