> Technically yes, the way things are in mame is indeed upside down; think about how a > raster screen is drawn to see why.
I'm not sure there is a technical explanation for why it would look like any of the ways scanlines are generated.
They'd only be upside down if it worked like paint that slid down the screen. If a monitor is out of focus it will affect the scan lines above and below as much as each other. Something like: