Star Tech Journal

Mediuni Resolution Monitors
James Beck
Greater Southern
Atlanta, Georgia
QUESTION
What is it and how does it differ from regular
low res monitors. Can a regular PCB feed a
med res monitor?
ANSWER
A "standard" monitor has specs that are
close to NTSC (National Television Stan-
dards Code) standards. That is a l 5KHz
horizontal sweep and a vertical rate of 60Hz
(non interlaced). These frequencies define
the total number of lines that are displayed
on the CRf. Then there is dot pitch, that is
the smallest discrete group ofRGB phospho-
rous that is on the face of the CRf itself. That
defines the smallest "clean" pixel that can be
enabled. The dimension of .41MM or so is a
"normal" pitch. In a game, the sync chains
and RGB outputs are designed to operate
within these specs.
MEDIUM RES
Now comes "Medium" resolution as opposed
to the above standard resolution. First you
up the horizontal frequency. That means
you get more horizontal lines on the screen
per each vertical scan. Sometimes the verti-
cal rate is increased too. 25Khz horizontal
rates are not uncommon. To take advantage
of the higher number of lines the dot pitch is
decreased so each individual pixel is
smaller. Hence, the resolution is higher. So
on and so forth, into higher and higher
frequencies.
COMPATIBILITY
The most obvious problem you see here is
that due to frequency incompatibilities you
can't put a standard res monitor into a
medium res game. Anyone who has tried
swapping with any of Atari's games like
Sprint will first notice that there are two
scrunched pictures on the screen. The
boards are putting out at a higher rate and
if the monitor does sync to one of the har-
monics then you end up with funny results.
It works in the opposite direction too. A
medium res monitor can't be properly driven~
by a standard set of boards.
RASTliiR UNE
HORl?.ONTAL SYNC
VfRTlcAL :S'iNL
BOTTOM LINE
To sum it up. the monitor and the boards
have to be matched to obtain the higher
resolutions and the matched set usually has
to remain together.
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