Ehring FDC4 Diskdrive Controller      and partially AP53 from IBS ( similar layout but different eproms )    Page No.:H085
			FDC4: Difference to recognize the diffent kind of controller: If you look at the pins used to connect the Apple DISK II drives you will recognize, that at the bottom area of the FDC4 at the right connector there is no area with 6 solderpads for jumperblock, while at the AP53 that area is present. In general it might be stated that the FDC4 is a "copycat" from the IBS AP53 controller except of the fact that both controllers differ by the contents within the eprom. This causes, that patch software for FDC4 won´t  work correct with the AP53 and vice versa. I also can´t make any kind of prediction about the behaviour of the AP53 if a eprom of the FDC4 is inserted. Up till now i have never tested that behaviour, if a copy of the FDC4 eprom is inserted in the AP53.   IBS AP53:
			circuitplan:
			manual für Patch165 Disk:
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