Connector:2nd disc drive (CPC664, CPC6128, CPC6128+)

The following table lists the signal on the "2nd Disk Drive" connector on the back of the CPC664/CPC6128/6128plus.
Signal names in simple brackets show the meaning the signal has today. For your convenience, the pin no. are given as specified in the Shugart standard first, followed by the pin no. as assigned by Amstrad and shown in the manual.

Note that pins 35 and 36 (Amstrad CPC enumeration) exist on Schneider CPC6128 only due to the use of a 36pin Centronics connector.
For a maximum confusion, Amstrad has completely changed the pin out on the 6128plus

Pin No. (Shugart)	Pin No. (CPC)	Pin No. (6128plus)	Signal Name	Description
n/a	"35"		N/C	Schneider CPC6128 only
1 (red wire¹)	34	n/a	GND	Ground
2	33	1	N/C (/REDWC)	Density Select 1=Low/0=High
4	31	3	N/C	Reserved
6	29	5	N/C	Reserved
8	27	7	/Index	0=Index
10	25	9	N/C (/MOTEA)	-/- (0=Motor Enable Drive 0)
12	23	11	/DRVSB	Drive Select 1
14	21	13	N/C (/DRVSA)	-/-(Drive Select 0)
16	19	15	/MOTEB	0=Motor Enable Drive 1
18	17	17	/DIR	0=Direction Select
20	15	19	/Step	0=Head Step
22	13	21	/WDATE	Write Data
24	11	23	/WGATE	Floppy Write Enable, 0=Write Gate
26	9	25	/TRK00	0=Track 00
28	7	27	/WPT	0=Write Protect
30	5	29	/RDATA	Read Data
32	3	31	/SIDE1	0=Side 1 Select
34	1 (blue wire²)	33	/RDY (/DSKCHG)	0=Ready (1=Disk Change/0=Ready³)
n/a	n/a	35	N/C
All others (odd)	All others (even)	All others (even)	GND	Ground

¹: Assuming you are using a cable which is made to match the Shugart standard on the floppy side.
²: Original cables from Amstrad/Schneider had blue wires to mark pin 1 (which is pin 34 in Shugart standard).
³: Although it might look like it, /RDY and /DSKCHG are not compatible. The CPC expects the drive to become ready (=0) by itself, while the DSKCHG signal stays high until confirmation through the PC, so the drive will never become RDY.

Except for the hint in note 3, a PC floppy can be directly operated on this connector, as long as you keep attention to the fact that the red wire of a PC floppy cable which is unchanged on the floppy side belongs on pin 34 of the CPC connector. Some drives can be jumpered to output the desired /RDY signal, some can at least be soldered. Others can be operated by "tuning" the cable. See 3 1/2" & 5 1/4" Disk Drives for more detailed instructions, incl. Side Switch.