(Active
Lines x Refresh Rate) / Total Number of Lines = % Active
Lines
254 lines x 53.2 Hz = 13619.2 total number
of active lines
Since the lowest 25kHz resolution is 384
lines, we can easily deduce that MK runs on a 15.720 kHz
CRT, so
13512.8 active lines / 15720 lines = 86%
active lines
From our list below we can see that 85%
is the closest mode.
192
active lines / 262 total number of lines = 73%
224 active lines / 262 total
number of lines = 85%
240 active lines / 262 total
number of lines = 91%
384 active lines / 416 total
number of lines = 92%
So, we can now safely conclude that the
Mortal Kombat series was designed for a CRT that ran the
popular mode
262 lines (224
active + 38 blanking) x 60 Hz = 15.7 kHz
This information also tells us that if
we configure a 15.7 kHz arcade monitor for
262 lines (240
active + 22 blanking) x 60 Hz = 15.7 kHz
that all the Mortal Kombat games will have
either the incorrect refresh rate, require stretching, or
will have borders, depending upon your setup. Likewise,
it also lets us know that if we configure a 15.7 kHz arcade
monitor for
262 lines (224
active + 38 blanking) x 60 Hz = 15.7 kHz
that all the Mortal Kombat games will run
true to the originals, with the correct refresh rate and
no borders or stretching. So what's the best mode to run
a 15.7 kHz monitor at?
If your 15.7 kHz monitor supports both
modes (which it should) then it really depends on where
your preferences lie. If you choose x224
at 60 Hz then more of your games will be in vertical synchronization.
If you choose x240 at 60 Hz,
then vertical games (run horizontally) will look nicer,
especially many older ones, like pacman, mappy, galaga,
etc. Why?
Well, all of these games used 288 columns,
and if you play a vertical game on a horizontal monitor,
then the columns become rows, so 288 columns becomes 288
rows. And if we do a little math
(15720 lines / (50 - 60)Hz) x 91%
active lines = 288 - 240 lines
we find that a 240
line setup can run all of your favorite < 288 column
vertical games on a horizontal monitor. Granted, they won't
be at the correct refresh rate, so your games will be out
of vertical synchronization, but at least none of the games
require line whacking or interlacing. If you choose 224
lines at 15.7 kHz then you have a range of
(15720 lines / (50 - 60)Hz) x 85%
active lines = 268 - 224 lines
As you can see, 288 column vertical games
take a whacking here, 20 lines need removing. But if your
willing to push your vclock down to 47 Hz, then
(15720 lines / (47 - 60)Hz) x 85%
active lines = 286 - 224 lines
all your 288 column games look groovy again.
If you did the same thing on a 240 line setup, you'd max
out at 306 lines. Naturally, the reverse of all this holds
true if you run horizontal games on a vertical monitor.
With a few more calculations we can also
see that
240
lines x 60 Hz - 224 lines x
60 Hz = 1 kHz
a 1kHz horizontal clock range enables us
to perfectly emulate any game between 224
- 240 lines.
It would take a hard core amount of underclocking,
overclocking to get 192 line
modes, so these games will either be stretched or have borders.
Be aware that the border hit is large here. On a 240
line setup, around 20% of your screen (192
/ 240 = 80%) and on a 224
line setup around 15% of your screen (192
/ 224 = 85%).
In order to emulate the two last modes
on a 15.7 kHz monitor, you'll need to half the games refresh
rate to 25Hz - 30Hz (i.e. interlace), which will just double
the number of lines at any hclock, so if you have a typical
240 line setup then you will
have the following interlace range
2 x (288 - 240)
lines = 576 - 480 lines
Notice that this takes care of vector games
quite nicely, but that 384
line modes will also require stretching or borders (be aware
that the border hit is large here, around 20% of your screen
(384 / 480
= 80%).
But what if happens if you run all these
modes on a 25 kHz monitor?
Well, on an ordinary 25 kHz arcade monitor
we have the following range to work with
(24960 lines / (50 - 60)Hz) x 92%
active lines = 460 - 384 lines
Obviously, a 25 kHz CRT can perfectly emulate
384 lines with
416 lines (384
active + 32 blanking) x 60 Hz = 25.0 kHz
But what of the other four modes?
192
line modes run perfectly double scanned or double pixeled
(192 lines x 2 = 384
lines). Vector games will require some line sacrifices,
however. Around 20 lines need to be whacked (480
- 460 = 20). If you underclock your refresh rate to 48 Hz,
though, then you won't have to sacrifice any lines
(24960 lines / 48 Hz) x 92%
= 480 lines
For the same reason, underclocking to 48Hz
means all your 240 line games
will run well double scanned (or double pixeled), though,
obviously the vertical synchronization will be off. If you
want your 240 line games in
vertical sync, then you'll have to stretch them or take
on a huge border, almost 40% of your screen (240
/ 384 = 62%). 224
line modes run great double scanned at 448 lines, but like
240 line modes, if you want
vertical sync you'll have to stretch them or take on an
even larger border, slightly over 40% (224
/ 384 = 58%).
How do you configure all of these modes
to run on a D9200?
First off, the listed specifications for
the D9200 on Wellsgardner's web site are a little misleading
/ confusing. The D9200 supports arcade boards that operate
between 15.75 - 31.5kHz, but it does not support the entire
range 15.75 - 31.5kHz. The D9200 is really a fixed frequency
monitor that supports hclocks at 15.75kHz, 25kHz, and 31.5kHz
with a 1-2kHz error margin at each frequency. This error
margin varies from D9200 to D9200, as some D9200 owners
have reported success with frequencies mine can't handle.
It's only fair to say, that mine was one of the very first
ones off the line. When I ordered it, they hadn't even started
production.
From the above calculations we know that
a 1 kHz horizontal clock range will enable us to emulate
any mode between 224 and 240
lines. This means that on the D9200 you need to a 1 kHz
hclock range near 15.75 kHz. How far you choose to push
your monitor is up to you, but from the conversation I had
with the engineer at Wellsgardner I feel quite safe with
a 1.5 kHz range at each popular hclock. So with this in
mind, I chose the following setup.
192
x 60 Hz = 13 kHz (doublescaned to 384 lines at 26 kHz)
224 x 60 Hz = 15.25 kHz
262 lines (230 active + 32 blanking) x 60 Hz = 15.72 kHz
(reference mode)
240 x 60 Hz = 16.3 kHz
384 x 60 Hz = 26.0 kHz (reference
mode)
480 x 60 Hz = 32 kHz (reference
mode)
pclock 6-90
hclock 15.25 -16.75, 24-26, 31-32.
vclock 50-90
If you know much about emulation, the
above numbers pretty much speak for themselves. Only one
mode is not perfectly emulated, and that's x192
which is just double scanned. If you bring your lower hclock
range up to 16.75 kHz, you will also get all the weirdo
modes that operate over 240.
There aren't many, but my D9200 handles them quite nicely,
and, like I indicated earlier, mine was one of the first
ones off the line.
Also, some are saying that they can run
their Windows setup at 800x600. I don't really recommend
this, as this overclocks the D9200 well beyond 1-2kHz.
|