LCD Pains

[Rick]

I'm having some trouble getting some refurbished LCD screens to work with multi-arcade PCB's that output 640x480 resolution. I think I know the answer, but I'm hoping that someone may have seen this issue previously, and could offer up some solutions.

When I attach the VGA cable to a newly acquired 17"/19" LCD, many will show the image about 1/4 of the way down the screen, even after clicking auto-adjust. In the menu, I can usually use the horizontal control to bring the picture *almost* all the way to fill the screen, and then, I have to set the 'clock' setting that will stretch the picture to fill the screen. (Although, there's still about 3/8" of black space along one side that the picture won't fill.)

That's what happens on some of the 17" Dell LCDs I've been working with. On other manufacturers, the monitors won't hold the settings once I turn the power off. (Meaning, if I want to play on one, I have to go through the menus to fit the picture to the screen every single time.)

Does anyone have some ideas to help fix this? (Or, is "you gotta find the right monitor that supports the old 640x480 right out of the box" the simple, in-your-face answer?)

Thanks!

[obcd]

Are you using the monitors in portrait (vertical) mode?
The way you describe it, it's like you are showing the 640x480 4:3 image on a 16:9 monitor. If that's the case, you can either stretch the image to fill the full screen or you have 2 black unused regions. If you stretch the image, a square will become a rectangle, so the result is not very nice.
Another thing with lcd monitors is that they only produce a sharp image when you feed them the native resolution of the lcd panel. This is normally the maximum resolution the screen can handle. In that case, every pixel gets it's unique color information. If you feed a lower resolution, the monitor electronics has to do some interpolation between pixels. Not all monitors handle this equal well, as they assume you will always use the monitor at it's native resolution. Another bad issue with lcd's is that they sometimes show the picture with a small delay. For normal computer work, that's not a problem, but on gaming, every milli second counts. Due to all this, most people prefer an old fashion picture tube monitor in their arcade cabinet. 

[Rick]

Are you using the monitors in portrait (vertical) mode?

Yes. The multi-arcade PCB I'm using is a vertical 60-in-1 iCade board.

The way you describe it, it's like you are showing the 640x480 4:3 image on a 16:9 monitor. If that's the case, you can either stretch the image to fill the full screen or you have 2 black unused regions. If you stretch the image, a square will become a rectangle, so the result is not very nice.

I'm not. I only use 4:3 LCD monitors. These are going into bartop systems, with multi-arcade PCB's only. I don't do MAME configs presently. (Or, this would be a much simpler solution.)

Another thing with lcd monitors is that they only produce a sharp image when you feed them the native resolution of the lcd panel. This is normally the maximum resolution the screen can handle. In that case, every pixel gets it's unique color information. If you feed a lower resolution, the monitor electronics has to do some interpolation between pixels. Not all monitors handle this equal well, as they assume you will always use the monitor at it's native resolution.

I think this is the issue. I'm pretty sure I've used some other, older, off-brand LCD's which handled the boards perfectly, and this has probably been because they were from an age when 640x480 was still a usable configuration. I'm thinking that the new LCD's I'm using are simply "too new", and are not well suited to the lower resolution requirements.

[obcd]

Monitors have a small buildin eeprom that contains the possible acceptable resolutions.
Maybe pc's read that information and adjust their resolution accordingly.
I am just unsure how they handle it for their bios setup screens.
If those are still 640 x 480 (I am talking about older ones without graphical bios setup), you would expect that monitors
should still support them as well.
The screen I currently use has a native resolution of 1680 * 1050.
If I run dosbox and set it fullscreen using <ALT> <Enter>, the monitor OSD tells me I am running a resolution of 640 x 480 x 60Hz
I am having a black border left and right due to my monitor not being 4:3 aspect ratio. If I remember well, there is a setting on the monitor to strech such an image or show it with the black borders.
I will check what resolution my pc uses in it's bios setup.
Using mame and a pc will make things a bit more expensive. Maybe a solution with an arm board like the raspberry would be an option as most games on the 60 in 1 are rather old, so they can be emulated without much cpu power. You will still need a proper way to interface your controls. A teensy or arduino board could do this rather cheap if you don't intend to make a 4 player control panel. You have the boards dedicated for this purpose, but they are more expensive. Be aware that the raspberry only has a hdmi output. (and composite yes I know) So, most older monitors will require a hdmi 2 vga converter with them. A pc can emulate more modern games, but an arm based setup has the advantage that you only need to prepare it's configuration once since you can rebuy identical hardware when needed. To my knowledge, most modern gpu's can handle the scaling in hardware.
One thing at a time I guess. Will check if pc bios is still 640 x 480.