The Special addresses are used only on CPC 664/6128 and only if the Vortex drive includes an FDC chip.
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The pictures of X drive has a different PCB than the PCB are not clear. There appears to be a jumper and a PAL type chip next to for the S, the FDC. The manual mentions describes connecting the DDI-1 interface to the X drive interface and a 'decoder-ROM' so perhaps this is in which defines the PALI/O decoding?