EDIT: ok..just updated to the latest FS-UAE with the Launcher.. I like the interface. Time to test :-)
EDIT 2: meh. not that great. Sound gets choppy, game lags as if my system is too slow. (SideWinder was the test game).
EDIT 3: lol...ok, if I use it in A4000 68040 mode, much smoother as if I was using an A500.
Hi, Amiga emulation at highest accuracy is a bit demanding. If you set accuracy to "less accurate" in FS-UAE Launcher (corresponding to FS-UAE option "accuracy = 0"), Amiga 500 emulation will no longer be cycle exact, and will require a lot less CPU to emulate. For most games, this is not a problem, and should generally be much more compatible with games than using the A4000/040 model (A4000 emulation is never cycle exact, which is why it runs faster).
Another thing that will make FS-UAE run lighter is to disable syncing to the display refresh. In the launcher, you can open the settings dialog (the rightmost toolbar icon), go to "Custom Settings", and put in this line:
video_sync = off
Not directly related to your case, also note that 68020 emulation is much more demanding than 68000, so it's normally a good idea to use A500/A600 rather than A1200 if the game does not need or benefit from the latter.