The Falcon *can* do just about any resolution ever, thanks to the programmability of the Videl chip. It's almost as versatile as the GTIA in the old 8-bits...
Of course, TOS 4 sucks so badly that Atari made these modes inaccesible from the desktop...
That's what BlowUp, ScreenBlaster, Videlity etc. do - I tried a weird software one time, I can't remember it's name, but it gave me like 1024x240 on my SC1435! The resolutions and frequencies you can get are limited by your monitor, and also the amount of CPU bandwidth the Videl chip can grab. That's how some of the screen expander hardware works - it basically speeds the Videl chip.
