It's two stacked boards with the eprom (a 32 pin eprom in a TSOP-32 package) on the bottom of the lower board. It switches to the NOS tune at wide open throttle above a certain RPM when wired to a WOT switch. The ECU should work fine while the first (default) tune is active and you don't need to have any wires connected to anything to run it that way. You should still be able to connect to the ECU and see all the data information using software (other than nistune).