On another note, I have verified that the 5B has the noise and envelope features of the YM2149F. If you want to try this yourself (i.e. if you happen to own Gimmick!) this is the code/NES/etc. I tested this with: http://dl.dropbox.com/u/883356/swap_tests.zip
NSFPlay has good emulation of this chip. So does Nestopia. A lot of other emulators don't implement noise/envelope or implement them incorrectly, because the Gimmick! game didn't use them.