IBM 770 manual System Board, Part, UltraBay II Connector Pin Assignments, Signal, Feature

Pin	Signal	I/O	and	Feature
51	DD15	I/O
52	GND	GND
53	-UBAY_HDD	I
54	DMARQ	I
55	GND	GND
56	-DIOW	O
57	GND	GND
58	-DIOR	O
59	GND	GND
60	IORDY	I
61	CSEL	O
62	-DMACK	O
63	IRQ	I
64	-IOCS16	I
65	DA1	O
66	-PDIAG	I/O
67	DA0	O
68	DA2	O
69	-CS1	O
70	-CS3	O
71	-DASP	I
72	-MCS	O
73	CD_MUTE	I
74	AUDIO_RTN	I
75	CD_L_IN	I
76	CD_R_IN	I
77	GND	GND
78	GND	GND
79	UBAYID3	I
80	UBAYID4	I
Figure	2-8 (Part	2	of	2). UltraBay II Connector Pin Assignments

2-14 System Board