That's what I thought it was supposed to be, but DuckHunt keep coming up at a much smaller resolution.
Do you have 'switchres 1' set in mame.ini?
I'll have to check when I get home tonight. Which way should it be set?
[no]switchres
Enables resolution switching. This option is required for the
-resolution option to switch resolutions in full screen mode. On many
modern video cards with hardware stretching support, there is little
performance penalty at higher resolutions, so it is nice to be able to
get rid of the monitor resync time when you run in full screen mode.
This is also useful on LCD displays with a fixed resolution. The
default is ON (-switchres). This option requires -ddraw.