CableWholesale.com has a nice archive of technical articles about cables, connectors, how to choose and use them, etc.

This page describes data cable connectors and their pinouts. See the audio-video cable page for descriptions and pinouts for HDMI cables. Jump to a cable type:

EIDE / PATA Cable Pinouts

What shall we call these devices....

In the beginning, or at least around 1986, was Western Digital's Integrated Drive Electronics (IDE) interface. That defined the low-level connection from a computer system board to a disk storage device. IDE refers to the disk controller being integrated into the drive and IDE providing an interface to a computer bus, initially the ISA bus. The host computer sees the storage device as an array of 512-byte blocks with a simple suite of interface commands.

That led to AT Attachment and AT Attachment Packet Interface standards, so ATA/ATAPI is a complicated but accurate designation.

In 1994 Western Digital introduced Enhanced IDE (EIDE) or ATA-2 drives.

Roughly 2007-2009 Serial ATA or SATA largely replaced ATA/ATAPI technology on motherboards, leading to ATA being renamed PATA for Parallel ATA. SATA uses the same command set as PATA, but it uses high-speed serial cables moving data at 1.5, 3.0, and 6.0 Gbps.a

PATA cable and plug. This is an old cable, a non-DMA cable with just 40 conductors. Note the notches and bump forcing it to only be inserted in the proper orientation. The contacts are numbered:
1 3 5 . . . 37 39
2 4 6 . . . 38 40

PATA Cable Pinouts

DD0 - DD15 — Data line 0 through 15.

IOCHRDY — I/O channel ready.

CS — Cable Select.

With the arrival of the Ultra DMA/33 mode, the cable went from 40-conductor to 80-conductor ribbon cable. The added 40 conductors are all ground lines, reducing crosstalk of the higher speed signals from what would have been adjacent conductors on 40-conductor cables.

1	3	5	7	9	11	13	15	17	19	21	23	25	27	29	31	33	35	37	39
RST	DD7	DD6	DD5	DD4	DD3	DD2	DD1	DD0	GND	DDRQ	I/O W	I/O R	IOCHRDY	DDACK	IRQ	ADDR 1	ADDR 0	Chip select 1P	Activity
GND	DD8	DD9	DD10	DD11	DD12	DD13	DD14	DD15	VCC in	GND	GND	GND	CS	GND	N/C	DMA66 detect	ADDR 2	Chip select 3P	GND
2	4	6	8	10	12	14	16	18	20	22	24	26	28	30	32	34	36	38	40

ATA/IDE disk drive, data and power connectors.

PATA disk drive. PATA data connector at left. Power connector at right. Six pins to add a jumper to select master versus slave device between them. Notice that pin 20 is missing. Also see the notch at top center in the black plastic shell to made with the bump on the connector, forcing correct orientation.

Pin 20 is usually not there, it may be a blank spot on the plug and missing a pin on the drive or motherboard connector to force plugging it in correctly oriented. But some flash drives use it to supply VCC to the drive.

Pin 28 is connected at the motherboard and master drive (far end) connectors, but not at the slave drive (middle) connector.

Pin 34 is connected normally (that is, to conductor #34) at the motherboard and slave drive connectors, but connected to ground within the motherboard connector.

Standard	Other names	Transfer modes (MB/sec)	Standardized
ATA-1	ATA, IDE	PIO 0, 1, 2 (3.3, 5.2, 8.3 MB/sec)	1994
		Single-word DMA 0, 1, 2 (2.1, 4.2, 8.3 MB/sec)
		Multi-word DMA 0 (4.2 MB/sec)
ATA-2	Fast ATA, Ultra ATA, EIDE, Fast IDE	PIO 3, 4 (11.1, 16.6 MB/sec)	1996
ATA-2	Fast ATA, Ultra ATA, EIDE, Fast IDE	Multi-word DMA 1, 2 (13.3, 16.7 MB/sec	1996
ATA-3	EIDE	Like ATA-2 but without single-word DMA modes	1997
ATA/ATAPI-4	ATA-4, Ultra ATA/33, UDMA/33	Ultra DMA 0, 1, 2 (16.7, 25.0, 33.3 MB/sec)	1998
ATA/ATAPI-5	ATA-5, Ultra ATA/66, UDMA/66	Ultra DMA 3, 4 (44.4, 66.7 MB/sec)	2000
ATA/ATAPI-6	ATA-6, Ultra ATA/100, UDMA/100	Ultra DMA 5 (100 MB/sec)	2002
ATA/ATAPI-7	ATA-7, Ultra ATA/133, UDMA/133	Ultra DMA 6 (133 MB/sec)	2005

PATA data cable. Left to right:
Master drive connector
Slave drive connector
Motherboard connector

SATA Cable Pinouts

1 TB disk drive with SATA power and data connectors.

Disk drive with SATA data (center) and power (right) connectors.

SATA power connector

The contact areas on the pins are small, so multiple pins are ganged together for ground and the various voltages.

Pin	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
Function	3.3 V			Ground			5 V			Ground	Staggered spinup	Ground	12 V

SATA slimline power connector

Used for smaller devices, such as notebook drives.

Pin	1	2	3	4	5	6
Function	Device present	5 V		Diagostic	Ground

SATA micro power connector

Used for 1.8-inch drives with SATA 2.6.

Pin	1	2	3	4	5	6	7	8	9
Function	3.3 V		Ground		5 V		reserved	vendor specific

SATA data connector

Pin	1	2	3	4	5	6	7	8
Function	Ground	A+ (Transmit)	A- (Transmit)	Ground	B- (Receive)	B+ (Receive)	Ground	coding notch

First-generation SATA, now called SATA 1.5 Gbit/s, moves data at 1.5 Gbit/second. The data encoding overhead reduces the actual throughput to 1.2 Gbit/s.

SATA 3 Gbit/s doubles the data transfer rate and adds command queueing.

The final SATA 6 Gbit/s specification was released in 2009. However, mechanical drives can barely saturate a SATA 3 Gbit/s link, so there will be little market for SATA 6 Gbit/s until drive I/O speed increases significantly.

Two SATA power cables.

SATA data cable.

USB Cable Pinouts

USB cable with Standard A and Standard B connectors.

USB cable, Standard A connector at left and Standard B connector at right. The contacts are numbered as laid out in these tables.

These are laid out here as viewed looking into the plug:

Standard A

Pin	4	3	2	1
Function	V-	Data+	Data-	V+

Standard B

Pin	1	2
Function	V+	Data-
Function	V-	Data+
Pin	4	3

Floppy Cable Pinouts

Yes, these are terribly archaic, but to be complete....

Drive A (at end of cable)

1	3	5	7	9	11	13	15	17	19	21	23	25	27	29	31	33
Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground
Density 1=Low 0=High	N/C	N/C	Index	Motor enable drive 0	Drive select 1	Drive select 0	Motor enable drive 1	Direct select	Head step	Write data	Floppy write enable	0=Track 00	0=Write protect	Read data	0=Head select	1=Disk change 0=Ready
2	4	6	8	10	12	14	16	18	20	22	24	26	28	30	32	34

Drive B (at middle of cable)

Lines 9-16 are reversed

1	3	5	7	9	11	13	15	17	19	21	23	25	27	29	31	33
Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground	Ground
Density 1=Low 0=High	N/C	N/C	Index	Motor enable drive 1	Drive select 0	Drive select 1	Motor enable drive 0	Direct select	Head step	Write data	Floppy write enable	0=Track 00	0=Write protect	Read data	0=Head select	1=Disk change 0=Ready
2	4	6	8	10	12	14	16	18	20	22	24	26	28	30	32	34

Floppy data cable above, and PATA data cable below. Notice that the PATA cable is limited to 18" total length, and also notice the floppy cable's twist between the Drive A and Drive B connectors. Left to right on the floppy cable:
Drive A connector
Drive B connector
Motherboard connector

Floppy data cable connector, Drive A connector at the far end, just beyond the twist of conductors 9-16. Note the notches and bump forcing it to only be inserted in the proper orientation. The contacts are numbered:
1 3 5 . . . 31 33
2 4 6 . . . 32 34