There is only 2 adapters for A3640 that I know to work.
XCalibur, which adds FAST RAM and 33MHz 040
Quaddoubler, 50MHz 040 (can be used with XCalibur)
Both cost more than a WarpEngine 040 or Apollo 4040
The A3640 really is a POS though, cripples the 040. If that is all you've ever used in your Amiga, you've not lived.
