224/239 lines test ROM?

I'd like to run a test ROM on a real SNES, which can switch between 224 and 239-line modes. I want to see exactly which scanlines are the extra ones in 239-line mode. Does anyone know whether such a program already exists? Or is that information already known? I'm thinking about the scanlines as output to the TV, not necessarily those from the point of view of the SNES program.

In other words, I'd like to determine exactly how many scanlines above and below the normal 224-line active area are used in 239-line mode.

Try this, hold the B button to toggle overscan.

Thanks very much for that. Did you code it youself? Mind if I share the link elsewhere? It showed up a problem with the GTK version of Snes9x so it would be useful when reporting the issue.

You're welcome, yes I threw it together in C, feel free to share it. Out of curiosity, what's the problem with it in snes9x gtk?

I'm interested in knowing this too. From what I heard, the extra lines are from the bottom down, but the TV might display it centered, depending on how the sync signal works.

When the mode changes from 239 to 224 lines, the image in the lower lines remains there. To show the problem enable "Use overscanned height" in preferences then load your test ROM. Press and hold B to use 239-line mode. Release B to return to 224-line mode, and the bottom of the display (where lines 224-238 were) still contains that green colour.

Yeah I see, the emulators I've tested with seem to handle the window and/or image resize properly.

That should be the case yes, I updated the binary (changed timings a bit) to better reflect this behaviour.