Burst mode is where you can transfer an entire cacheline (16-bytes) with only one setup cycle(s), as opposed to having to call out each 32-bit read/write. i.e. after the setup then each cycle you squirt another 32 bits down the bus for the next 3 cycles. This only works on a synchronous bus obviously, and the 68040/060 and 68020/030 buses are different in other ways as well. The A3000/A4000 fast slot is on a 68020/68030 bus. This is normally only handled by the caches but you can explicitly take advantage of this as well on 040/060 with MOVE16.
The A3640 has no local memory to burst to, and runs on a dissimilar bus. Even you run it synchronous to the motherboard bus (Speedgeek does this to minimize wait states), it has only bare-bones glue that will not let you burst across it.
