Also the results vary depending on the games you're trying to emulate, e.g. Yoshi's Island will still be unplayable, while Super Mario World and Donkey Kong Country will run pretty much perfectly.
At first some general things to improve the emulation speed which should be widely known by now:
A Small Checklist To Improve The Emulation Speed With DreamSNES
In the options menu you change the following settings:
- Turn on CPU optimizations
- Turn off the Sound or set it to MONO
- Turn off Mode7 Interpolation
- Turn off Transparencies if not needed for the game
Now on to the 20% boost mentioned in my introduction:
European 50Hz PAL vs. US/JP 60Hz NTSC
If you use European PAL games instead of their American or Japanese versions you definitly will expierence a major speed boost of about 20% - thanks to the 50/60Hz difference between PAL & NTSC and just because emulating games that run at 50Hz is much easier for DreamSNES than emulating games that run at 60Hz.
That means all American or Japanese games that previously ran at 80% speed will run at 100% if you use their EU PAL version in DreamSNES.
If you are not sure what region your games come from, try using GoodSNES, a tool which renames and classifies your games.
GoodSNES is available here: http://www.allgoodthings.us/
Some more details about the reason why EU PAL emulation is so much more efficient with DreamSNES:
PAL games by Nintendo, Rare, Infrogrames, and other good European distributors and developers are 20% faster because their speed has been modified/optimized to match 50Hz. On DreamSNES these actually would ran smoother yet also faster than the US/JP versions of the same games.
Playing these games will offer 100% full speed emulation with very little frameskipping.
European PAL releases by smaller Japanese or American companies with small or bad European distributors miss the speed modification for the 60Hz -> 50Hz difference, thus they will run smoother with DreamSNES, but actually are slower than their US/JP original on a real machine.
Playing these games on DreamSNES will offer 100% speed with very little frameskipping but they'll be still be slower than on a real American or Japanese SNES.
I also posted the info at Dreamcast-Scene.com's Wiki along with some more general info about DreamSNES: