Is a 15/25 kHz monitor like a 15 kHz only? (for 15 kHz games)

[ebo0763]

Does a 27" 15/25 kHz monitor from a Golden Tee cabinet (for use with mame) can do the exact same thing as a 15 kHz only monitor when it's used for 15 kHz games. Meaning, if a 15 kHz game has 240 lines, will that 15/25 kHz monitor (when put on the 15 setting) will actually display 240 lines?

The reason I'm skeptical of this is because the tube is supposed to have a metal mesh or screen (behind the phosphorus) that determines the resolution. So if the the monitor is 25 kHz, it should have a certain amount of lines into it right? Then if it's 15 kHz compatible, it means it tries to fit the lower resolution into a higher resolution display and it wouldn't be a 1:1 pixel ratio.

I'm a bit confused and I don't want to make you biased but, dam I hope I'm wrong... hehe.

So ultimately, the question is, is it preferable to use a 15 kHz instead of a 15/25 kHz monitor for use of 15 kHz game?

Thanks.

[MonMotha]

You're probably thinking of the "dot pitch" of the tube.  Finer (smaller) dot pitches allow the monitor to resolve smaller details at higher resolutions but will result in overly emphasized scanlines at lower resolutions.  TV tubes, which are also used on monitors, tend to have fairly coarse dot pitch to make up for the imperfections of television, and this is also handy on low resolution arcade video signals.  CRT computer monitors have very fine dot pitches to allow them to be used at the higher resolutions computers run at.  Some later arcade monitors have tubes with a finer dot pitch than a typical TV tube, but still not as fine as a computer monitor.

There's also a shadow mask or aperture grill behind the tube phosphors that may be what you're thinking of, but those are by necessity matched to the phosphor dot pitch.

The neat thing about CRT monitors (and an effect not replicated by any other common display technology) is that they're truly capable of displaying any resolution within their capabilities.  Some later TVs scaled everything digitally, but arcade monitors don't do this.  They just take whatever you feed it and chuck it on the screen.  There's no 1:1 mapping between the displayed video and the dot pitch.  There's a visual interaction between them (noted above), but nothing more.

To answer your original question: In a nutshell, There's no difference between a 15kHz only monitor and a dual resolution or multisync monitor using the same or similar tube when displaying the same input.  You can use your dual resolution monitor on the 15kHz setting and enjoy all your games in their native resolution once you get it all set up.

[ebo0763]

This is awesome. Thanks you very much for your elaborate answer.

[ebo0763]

So I took a closer look at it while it's off and I can see vertical lines with the RGB colors. There's a column for red, one for green and one for blue. So does it mean that both 15 and 25 kHz have the same amount of verital lines (horizontal pixels)? Meaning from 15 to 25, there's only more horizontal lines and not vertical?

[MonMotha]

The phosphor arrangement on the front of tubes vary.  Some have the colors staggered, while others just have stripes.  Regardless, only areas actually hit by the stream of electrons that come from the back of the tube during operation will light up.  This stream only has limited height, and it scans horizontally across the screen, steps down a hair, then repeats.  This is what creates your scanlines.

The number of scanlines is determined only by the input signal.  How tall (or "thick") the scanline is will depend on several factors, mostly the dot pitch of the CRT, how high you've got the contrast knob turned up, and the condition of the tube.

Note that there aren't really any discrete horizontal pixels at all.  The monitor has no idea that there are discrete pixels horizontally.  All it sees are three color intensity signals that happen to have stairstep changes in it (which is where the pixel boundary is).

Again, there's no direct mapping between the phosphors on the front of the CRT and the actual displayed resolution.