several days ago the creator of the bsnes emulator released version 109 on his web site
one important part of the changelog for v109 of bsnes is the following:
added options to emulate bugs in ZSNES and older Snes9X releases to increase compatibility:
"No VRAM blocking" for older fan translations
"Echo shadow RAM" for older Super Mario World ROM hacks
"CPU fast math" for older homebrew
"Entropy: none" technically counts as well, for demoscene software made for SNES copiers
for example, I want to play some old SMW hacks like Big Boo's Revenge
or Mario's Treasure Hunt 1
or Mario's Treasure Hunt 2
, the "Echo shadow RAM" option must be turned on from the Compatibility menu of bsnes before loading any of these old SMW hacks - otherwise these games will not work correctly in bsnes and the sound may stop working altogether.
with the recent releases of bsnes & snes9x, old SMW hacks can be played in these emulators as long as the proper compatibility options are enabled.
Edit 9/21 - recently bsnes v110 was released with some important bug fixes