VGA Monitor Settings

[Lamaman1971]

Hi, I have hooked up a 14 inch VGA CRT to my MiSter via the analog VGA port and it looks great. I want to optimise the settings and I think the basic ones are letting me down. Its max resolution is 1280x1024 @ 60Hz so right now I am using setting #4 in the ini.

However, on the MiSTer information screen it tells me that its running at 60Hz Vertical but 108Mhz Horizontal (which seems a bit odd). The manual tells me that I should be running at 63.95Mhz.

Can anyone recommend a way of reconfiguring the ini to better reflect the capabilities of the monitor?

[FoxbatStargazer]

Here's an example info screen from the Genesis core running in video_mode=4

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  256x224   15.70KHz   59.9Hz
1280x1024  107.83Mhz   59.9Hz

The first line shows the core's original analog output resolution. The second line shows the scaler's output. You'll notice the middle number in the scaler line is in Mhz and not Khz. It is not the horizontal refresh rate as in the top line, but rather the pixel clock, which is sort of the rate at which all the video information as a whole has to be transmitted. This is an important number for the scaler because Mister has limits on how high it can push the pixel clock and modes 12 and 13 are approaching that limit, and its also relevant to digital displays in terms of whether they can even handle the incoming information rate. I don't think it's much of a direct limitation for CRTs which are more focused on horizontal and vertical refreshes as upper bounds.

[AmanoJacu]

When I use the Mister in my VGA CRT, I used the scandoubler option (forced_scandoubler=1) so the image I get is the one from the top line, original core analog output resolution, just doubled. To use the scaler, you should have vga_scaler=1, I tried it but I liked the other option better.

[FoxbatStargazer]

Oh right I was too busy explaining what the numbers meant. Yes if you have a lower resolution CRT like 1024p you are probably better off using the scandoubled analog output when you can (vga_scaler=0 forced_scandoubler=1, connected to VGA port on I/O board). While its more limited in terms of filters etc. it will deliver the sharpest, clearest results. But there are still cases where you may want vga_scaler, like using the menu core. You can make sections of the ini at the end apply settings only to a specific core by putting the core name in brackets, like

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[menu]
vga_scaler=1

Keep in mind now its much easier to create your own video modes now, like so

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; calculated mode: width,height,refresh[,flags]
;   video_mode=1920,1200,60
; flags - cvt=CVT timing, cvtrb=CVT-RB timing (default)video_mode=0

video_mode=800,600,60 -cvt

Generally for CRTs you will probably need -cvt for proper blanking. And as mentioned, vga_scaler=1 if you want this to apply to the I/O board's VGA port. If you are using an HDMI->VGA converter and want to use the analog scandoubled output, use direct_video=1 and forced_scandoubler=1 instead.

[Lamaman1971]

Thanks folks,

Those explanations make alot more sense. As it turns out, even with a good mess with the settings, my Minimig core was giving me ghosting whatever I did so I ended up using a HDMI to VGA adaptor for my CRT (which feels like a bit of a cop out, but the picture quality on my crt is way better).

I am left wondering if I have a poor quality Analog IO board to be honest.