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The Monitor FAQ

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menace:
Understanding vertical limits and sizing of arcade monitor screens Courtesy of WPCMAME:

There is one thing that you must understand about graphic cards. They can't control the distance between the lines on the monitor. Modern monitors can auto-adjust so that the image fills the entire vertical height but with an arcade monitor the only way to change the vertical size is the knob marked "Vertical Size" or "V.SIZE".

Normally when you put a game into a cabinet you adjust the monitor so that the image fills the entire screen. The problems start when you put a PC into the cabinet and switches between games with different vertical resolution. You don't want to mess with the V.SIZE knob every time.

What you have to do is to fix the number of lines you want your monitor to display and then accept that some games doesn't fill the entire monitor or are clipped at top/bottom. If you accept that the game display is a bit distorted you can use stretch but watch out for the refresh rate (more about that later).

So here is a little guide.
Look at what games you want to play and what resolutions they got. Most horizontal games use  224,240,248 or 256 lines. vertical games on a horizontal monitor use 256 or 288 lines.

Lets take two cases.
1. You don't play vertical games on the horizontal monitor but you do play some games with 248 lines.
To adjust your monitor, use a resolution with 248 lines and adjust the monitor so that the image fills the entire height. I don't know what pixelclock the  ArcdeVGA card uses for its resolutions so I can't help you adjusting the horizontal size. Best thing is probably to use 320x240 and then adjust the monitor so that the black borders on the sides are the same size as the ones on top/bottom. If you use advancemame use a resolution of 330x248 (4:3) and adjust it so that it fills the entire monitor.

Now with 248 lines on your monitor you will get black borders on all games that uses less than 248 lines. 240 line games will give you ~3% black borders and 224 line games give ~10%.

2. You want to play vertical games with 288 lines on your horizontal monitor. Adjust the monitor in the same way as above but use a mode with 288 lines (e.g. 384x288). Note that vertical games don't use the entire width of the monitor so it doesn't matter if you can't see the corners.
With 288 lines on your monitor you will get big black borders on all horizontal games. 240 line games will get 20% and 224 line games get 29% or almost a third!

I use around 280 lines (missing a few lines on vertical games) on my 25" monitor which means that horizontal games is the same size as on a ~20" monitor. I probably wouldn't set it up with more than 256 lines on a smaller monitor.

What about stretch then?
MAME got a feature that allows you to stretch/shrink the image to any size that you want. With that feature you can have all games fill the entire monitor but with a more or less distorted image. There is one thing to watch out for: refresh rate.
Arcade monitors got restrictions on what refresh rate you can use for different resolutions. Approx. values are
240 lines 60Hz
248 lines 57Hz
256 lines 55Hz
288 lines 50Hz
This means that if you adjust your monitor to 256 lines, a game that fills the entire height of the monitor (with or without stretch) can't use a refresh rate of more than 55Hz. The limit is 50Hz for 288 lines. The choice here is if you want the game to fill the entire height (with stretch) or if you want it to run at the correct refresh rate. Some games are more sensitive to differences in refresh rate than others. E.g. horizontal scrolling games will show tearing effects. Note that either the refresh rate is correct or not. It is not better to run a 60Hz game with 57Hz than 50Hz.
You can't run your vertical games at their correct refresh rate on a horizontal monitor. Fortunately these old games usually doesn't use scrolling. One exception is BombJack where the background will flicker if not run at 60Hz. For BombJack I use a special mode with 247 lines and 60Hz to avoid the flicker but I miss some lines at top/bottom.

Peter Baluk:
just another tip on degaussing a monitor.
place your game so it faces to the north or south when usind a degaussing coin as it will help in the process of degaussing as it lines up with the magnetic forces of the earth.

JoeB:

--- Quote from: skyhopper on February 19, 2004, 09:41:00 pm ---just another tip on degaussing a monitor.
place your game so it faces to the north or south when usind a degaussing coin as it will help in the process of degaussing as it lines up with the magnetic forces of the earth.

--- End quote ---

I thought this trick only works for really big monitors.

The biggest problem when it comes to monitor magnetic interference is the speakers.  Before installing speakers in a cab, test them out by bringing them within the install distance while the monitor is on.  Move it around the screen.  If you notice significant interference, forget about using those speakers!

Gideon:
Hi, I've got a question for the FAQ:  What is degaussing, and why would one want to degauss a monitor?  Please tell me, as I'm too embarassed to start en entire topic with this question.

menace:
Because your monitor operates by an electron gun firing electrons at a phosphor grid it uses magnets and magnetic fields to aim the electrons that are being fired.  When a monitor gets a foreign magnetic field applied, the guns go out of whack and you get discoloration.  the purpose of degaussing is to erase those errant fields so that the monitor only has its own magnetic properties governing.  Most monitors have built in degaussing coils which operate for a few seconds when initially turned on.  This way the electrons hit the screen where they were originally intended and the picture looks as it should.

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