MiSTer FPGA Forum

Vigilante (Japan, Rev D) - this is what the screen looks like from a fresh boot of the MiSTer connected to a CRT:

Notice how the screen is as it should be, according to my custom vertical and horizontal settings in the OSD.

If I turn the CRT off, then back on, this is what the screen looks like:

Note the black gap at the bottom of the screen (where I placed the red rectangle). The screen has shifted upwards.

I was not able to replicate this behaviour with other cores, although I didn't test many. For this reason, I am going to guess that this may be an issue with the core, rather than my CRT. I note that adjusting the offsets after turning the CRT off then on does not allow me to get back to the position seen in the first screen shot. Reloading the core also does not fix the issue. The only way to fix is to either switch the MiSTer off then back on again or switch to another core then back to the Vigilante core.

This is almost certainly something related to your TV, as there is no feedback channel from a CRT back to the MiSTer, so MiSTer has no way of knowing that you've done anything to your CRT (and thus cannot modify its behaviour on that basis).

However, as this is a Jotego core, I don't know whether he reads this forum; you may be better to check with his support channels (for example, I understand that there is a discord that he runs; I don't know the details however).

dshadoff wrote: ↑Sun Jul 30, 2023 3:10 pm

This is almost certainly something related to your TV, as there is no feedback channel from a CRT back to the MiSTer, so MiSTer has no way of knowing that you've done anything to your CRT (and thus cannot modify its behaviour on that basis).

If that was the case, then why are non of the other cores I tested affected?

Because most arcade games output slightly different frequencies, and your CRT may have issues locking on to some of them. When you turn the CRT off and on again while keeping the signal active, it could end up syncing to a different part of the image than it would if it was already turned on when the initial signal from the game reached it.

(Note: I’m not saying that this is exactly what’s going on here, nor that there couldn’t be an edge case bug in this particular core. Just that even if a number of cores are made by the same author, that doesn’t mean they all behave the same way on the output side)

Right. And it doesn't mean that your CRT is "bad", just that it isn't quite compatible.
You need to keep in mind that arcade cores had custom monitor sections in them, and many aren't compatible with regular NTSC (or even PAL) screens. Worse, some of them are nearly compatible (but not quite).

A lot of arcade games had to have their CRTs adjusted for that particular board when it was installed. It was expected since there wasn't really a standard.