A Moogle  🏳️‍🌈 💻 🎮 🎶 🇸🇪

I was wondering more about whether that screen is a different part of the framebuffer, or the other set of three boards. ;) IIRC, there are six FB boards. One set for Y,U,V, and another set for the back buffer.

There were definitely two frame stores available at the same time as you could use a 'reveal' brush to paint one into the other.

Yeah, that's what we're seeing in that screenshot. Rather than emulate the Combiner Card just yet, I'm simply chucking the monitor window, Frame Store I contents, and Frame Store II contents on-screen side-by-side, for debugging purposes.

Yes - the palette and menu could be overlaid over the top or the bottom of the video image (for obvious reasons)

Right. Each frame store had a usable 800x600 area, but during scanout, either the top 128 lines or bottom 128 lines would be fixed to scan out the palette or menu region rather than the corresponding lines in the store.

Pretty certain Paintbox didn't internally scale on input and output (particularly as it handled interlaced video)

I'm just going off of what the manual says, which is that each triplet of Frame Store cards forms a 640x1024 buffer which is remapped to 800x768 by a set of PROMs. With 128 for the menu boxes deducted, that's 800x600. The actual usable area is probably smaller than that.

Yep - wonder if it's square pixels 768x576 vs 648x486 for the 50Hz and 59.94Hz variants?