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Index

• Terms/Names and maximum Data Transfer Rate
• Different types of common SCSI Cables
• Different types of common connectors
• Compaq SCSI Controller Overview
• Installation
• Maximum Bus Length
• Max Number of devices per external bus
• Other and obsolete SCSI Terms
• Signals on the SCSI bus
• Glossary and links to other references

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Terms	Name	MHz	Bus Width	MB/s	MBit/s	Basic Host Adapter
SCSI-1	SCSI-1	5	8	5	40
Fast SCSI	SCSI-2	10	8	10	80	AHA-1540CP SINGL
Fast-Wide SCSI	SCSI-2 / SCSI-3	10	16	20	160	AHA-2742W KIT
Ultra SCSI	SCSI-3	20	8	20	160	AHA-2940 ULTRA S
Ultra-Wide SCSI	SCSI-3	20	16	40	320	AHA-2940UW SINGL
Ultra2 SCSI	SCSI-4	40	8	40	320
Ultra2-Wide SCSI	SCSI-4	40	16	80	640	AHA-2940U2W SGL
Ultra3 SCSI	Ultra160/m	40*2 1)	8	80	640	29160N
Ultra3-Wide SCSI	Ultra160/m	40*2 1)	16	160	1280	29160
Ultra4 SCSI	Ultra320	80*2 2)	8	160	1280
Ultra4-Wide SCSI	Ultra320	80*2 2)	16	320	2560

1) Ultra3 features the same base frequency as Ultra2 (40MHz) but transmits 2 bytes per data clock thus doubling the total throughput.
   This is the same technique used in SDRAM, DDR and RAMBUS Memory where one data word (8 or 16 Bits) is transmitted at the raising edge and one at the falling edge.
2) Ultra4 doubles the base frequency of Ultra2 (80MHz) and like U3 transmits 2 bytes per data clock thus doubling the total throughput vs U3.
   Ultra4 also features AAF (Adjustable Active Filter), QAS (Quick Arbitration and Selection). 
   This enables these fast speeds at these long cable lengths and decreases the overall latencies due to the protocol overhead.

Fast-Wide SCSI is actually SCSI-2, however many cable manufacturers refer to the 68-pin plugs as SCSI-3. This is by definition of the STA incorrect!
Most SCSI 1-4, 160/m Ultra320 Devices can be mixed on the same bus, however, the slowest device/controller determines the bus speed during negatiating and in some cases also during data transfers!
You can not mix single ended and High Voltage (HV) differential! But you can mix most LVD (Low Voltage Differential) and single ended devices. Please note, that Fast-Wide SCSI-2 is also sometimes called SCSI-3 (in particular when referring to the 68 HP connector).


You can also mix Wide and Narrow, Fast-SCSI2 and Ultra SCSI Compaq Pluggable drives.
However, The bus (all 16 Datalines) must be properly terminated and you can not plug in a Wide SCSI Drive into an old Narrow SCSI Server, since the connectors are too wide. If you use a Wide (68pin, 16Bit) to Narrow (50pin, 8Bit) Adapter, make sure that the termination is at the WIDE side of the bus.

There are some cases where for one or another reason you can not mix.
Here are some known examples:
Works: Smart 2P, Smart 2E, Smart 2DH Controller and 146742-004 (Narrow Fast-SCSI2) together with 272577-001 (Ultra Wide)
No good: Deskpro XL (Narrow Fast-SCSI2) with 199642-001 (Wide Fast-SCSI2 with adapter)
No good: Prosignia 200 SCSI (Ultra Wide) and 2-8GB DAT DRIVE 142019-001 (Narrow Fast-SCSI2 with adapter) with 242584-001 (Wide Fast-SCSI2)

Description	Length	Compaq Partno	Generic DELEC Partno
DB25 - SCSI1	0.9m		380-003-25
SCSI1 - SCSI1	0.9m		381-003-50
SCSI1 - SCSI1	1.8m		381-006-50
SCSI1 - SCSI2	0.9m		511-003
SCSI1 - SCSI2	1.8m		511-006
SCSI2 - SCSI2	0.9m		502-003
SCSI2 - SCSI2	1.8m		502-006
SCSI1 - SCSI3	0.9m		538-003
SCSI1 - SCSI3	1.8m	189632-002	538-006
SCSI1 - SCSI3	3.6m	189632-003	538-012
SCSI2 - SCSI3	0.9m		7332031
SCSI2 - SCSI3	1.8m		7332061
SCSI3 - SCSI3	0.9m		530-003-MM
SCSI3 - SCSI3	1.8m		530-006-MM
VHDCI - SCSI1	1.8m	295646-B21
VHDCI - SCSI1	3.6m	295647-B21
VHDCI - SCSI3	1.8m	295644-B21
VHDCI - SCSI3	3.6m	295645-B21
Internal Cables and Adapter
50pin ribbon	2 pos no Termination	137964-001
50pin ribbon	4 pos w/ Termination	212051-001
50pin ribbon	4 pos w/ Termination	212051-002
50pin ribbon	7 pos w/ Termination	149116-001
68pin ribbon	4 pos w/ Termination	189626-001
68pin ribbon	4 pos w/ Termination	189649-001
68pin ribbon	7 pos w/ Termination	189628-001
50pin - 68pin	Narrow 2 Wide Adapter	212055-001

(SCSI3 Refers to Wide 68pin Connectors rather than Ultra SCSI)

Name	Common Name	No of Pins	Application	Bus Width	SCSI Standards	Comment
D-Sub 25	Apple	25	External	8 narrow	SCSI 1+2	Primarily for Microtest Discport, ZIP drives and Apple Computers
50 Centronics	SCSI-1	50	External	8 narrow	SCSI 1+2+3	Most common for Scanners, Tapes and external CD-ROM's and other slower periphereals
50 HP	SCSI-2	50	External	8 narrow	SCSI 2+3	External Raid-Disks and high performance Tape Libraries
68 HP	SCSI-3	68	External	16 wide	SCSI 2+3	External Raid-Disks and high performance Tape Libraries
50pin ribbon	normal	50	Internal	8 narrow	SCSI 1+2+3	Standard internal narrow SCSI Disks, CD-ROM's, Tapes and optical disks
68pin ribbon	wide	68	Internal	16 wide	SCSI 2+3	Wide SCSI Disks and other high performance drives

The words "narrow" stand for 8 bits and "wide" is 16 bit. The majority of the millions of SCSI devices in use today use single-ended transceivers (Asymmetrical, ground referenced). Differential (symmetrical +-) devices, which provide for greater bus lengths, are typically used in applications which can properly bear the added expense.

A new transceiver technology, Low-Voltage Differential (LVD), will combine the best features of single-ended and high-powered differential transceivers. LVD will also enable higher speeds. To ease the migration to LVD, most new SCSI devices will support Universal transceivers which include both single-ended and LVD transceivers.

Compaq SCSI Controller

Part Number

Bus

Max Dev

Interface Protocol

Host Bus Transfer (MB/sec)

SCSI Transfer (MB/sec)

Host Bus

Internal SCSI Connector

External SCSI Connector

Wide SCSI

Software Incl.

# SCSI Channels / Cache

Plug and Play SCSI

187749-001

ISA

7

Programmed I/O ISA

Up to 3

Up to 10

16-bit

50-pin Fast SCSI-2

50-pin Fast SCSI-2

No

Adaptec EZ-SCSI Lite

1 / 0MB

32-Bit Fast-Wide SCSI-2/E

142290-001

EISA

7

32-Bit EISA

33

Up to 20

32-bit

50-pin Fast SCSI-2

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2 Yes

Support Software CD

1 / 0MB

32-Bit Fast-Wide SCSI-2/P

199533-001

PCI

7

32-Bit PCI

133

Up to 20

32-bit

50-pin Fast SCSI-2

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2 Yes

Support Software CD

1 / 0MB

UltraSCSI

185250-001

PCI

7

32-Bit PCI

133

Up to 20

32-bit

50-pin Fast SCSI-2

50-pin Fast SCSI-2

No

Adaptec EZ-SCSI Lite

1 / 0MB

WIDE ULTRA Ultra2 PCI CONTR.

272514-001

PCI

7

32-Bit PCI

133

Up to 40

32-bit

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2

Support Software CD

1 / 0MB

Single CH Ultra2 SCSI Adapter 64

154457-B21

PCI 64

14

64-Bit PCI

533

Up to 160

64-bit

50 and 68pin Connector

unknown

Yes

Support Software CD

1 / 0MB

Dual CH Ultra3 SCSI Adapter 64

129803-B21

PCI 64

28

64-Bit PCI

533

Up to 160

64-bit

2*68pin Connector

2*VHDCI68-pin Ultra3-Wide SCSI

Yes

Support Software CD

2 / 0MB

Dual CH Ultra3 SCSI Adapter 64

348757-B21

PCI 64

14

64-Bit PCI

266

Up to 80

64-bit

2*68pin Connector

2*VHDCI68-pin Ultra2-Wide SCSI

Yes

Support Software CD

2 / 0MB

Dual CH Ultra3 SCSI Adapter 32

295554-B21

PCI

14

32-Bit PCI

133

Up to 40

32-bit

2*68pin Connector

2*VHDCI68-pin Ultra2-Wide SCSI

Yes

Support Software CD

2 / 0MB

SMART SCSI ARRAY CONTROLLER

142055-001

EISA

14

32-Bit EISA

33

Up to 10 / Channel

32-bit

50-pin Fast SCSI-2

2 * 50-pin Fast SCSI-2Cable

No

Support Software CD

1 / 2MB

SMART-2/E ARRAY CONTROLLER/E

194751-001

EISA

14

32-Bit EISA

33

Up to 20 / Channel

32-bit

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2

Yes (Narrow w/ includ. Adapter)

Support Software CD

2 / 4MB

SMART-2/P ARRAY CONTROLLER/P

194753-001

PCI

14

32-Bit PCI

133

Up to 20 / Channel (40 with flash update)

32-bit

68-pin Fast-Wide SCSI-2

68-pin Fast-Wide SCSI-2

Yes (Narrow w/ includ. Adapter)

Support Software CD

2 / 4MB

SMART-2/DH ARRAY CONTROLLER/DH

295242-B21

PCI

14

32-Bit PCI

133

Up to 40 / Channel

32-bit

68-pin Ultra-Wide SCSI

68-pin Ultra-Wide SCSI

Yes (Narrow w/ includ. Adapter)

Support Software CD

2 / 16MB

SMART-2/SL ARRAY CONTROLLER/SL

242776-B21

PCI

7

32-Bit PCI

133

Up to 40 / Channel

32-bit

68-pin Ultra-Wide SCSI and 50 pin

68-pin Ultra-Wide SCSI

Yes (Narrow w/ includ. Adapter)

Support Software CD

1 / 6MB

SMART ARRAY CONTROLLER 3100

295570-B21

Cpq Proprietary

21

64-Bit Cpq PL 6000 / 7000

266

Up to 80 / Channel

64-bit

68-pin Ultra2 via Motherboard

68-pin Ultra2 via Motherboard

Yes (Narrow w/ includ. Adapter)

Support Software CD

3 / 64MB

SMART ARRAY CONTROLLER 3200

295643-B21

PCI

28

32-Bit PCI

133

Up to 80 / Channel

32-bit

1/2 VHDCI ext or 1/2 68pin int.

1/2 VHDCI ext or 1/2 68pin int

Yes (Narrow w/ includ. Adapter)

Support Software CD

2 / 64MB

SMART ARRAY CONTROLLER 431

127695-B21

PCI 64

14

64-Bit PCI

266

Up to 160

64-bit

68-pin Ultra3-Wide SCSI

1*VHDCI68-pin Ultra3-Wide SCSI

Yes

Support Software CD

1 / 16MB

SMART ARRAY CONTROLLER 4200

295636-B21

PCI 64

56

64-Bit PCI

266

Up to 80 / Channel

64-bit

2*68-pin Ultra2-Wide SCSI

4*VHDCI68-pin Ultra2-Wide SCSI

Yes

Support Software CD

4 / 64MB

SMART ARRAY CONTROLLER 5302/32

166207-B21

PCI 64

28

64-Bit PCI

533

Up to 160 / Channel

64-bit

2*68-pin Ultra3-Wide SCSI

2*VHDCI68-pin Ultra3-Wide SCSI

Yes

Support Software CD

2 / 32MB

SMART ARRAY CONTROLLER 5302/64

124992-B21

PCI 64

28

64-Bit PCI

533

Up to 160 / Channel

64-bit

2*68-pin Ultra3-Wide SCSI

2*VHDCI68-pin Ultra3-Wide SCSI

Yes

Support Software CD

2 / 64MB

SMART ARRAY CONTROLLER 5304/128

158939-B21

PCI 64

56

64-Bit PCI

533

Up to 160 / Channel

64-bit

2*68-pin Ultra3-Wide SCSI

4*VHDCI68-pin Ultra3-Wide SCSI

Yes

Support Software CD

4 / 128MB

SHARED ARRAY CONTROLLER CR3500

388332-B21

Cpq Proprietary

13

Cpq Proprietary (Cluster)

320

Up to 80

prop

Integrated

Integrated

Yes

Support Software CD

1 / 128MB

INTEGRATED ARRAY CONTROLLER ROC

128293-B21

Cpq Proprietary

# int drvs (14)

Cpq Proprietary (ROC Slot)

133

Up to 80

prop

Integrated

0

Yes

Support Software CD

1 / 8MB

RAID LC 2

188044-B21

PCI

5

32-Bit PCI

133

Up to 80

32-bit

68-pin Ultra2-Wide SCSI

0

Yes

Support Software CD

1 / 8MB

The 2 most important Consideration on a SCSI Bus are:
1. Properly Terminate the Bus
2. Make sure every device has a unique SCSI ID

You must have a terminator (preferably active) on either end of the bus. They should be on the very extremes of the bus, and not somewhere in the middle or near the end. Keep in mind. There are only 2 terminators (not 1 or 3, simply 2). Most HA (Host Adapters) have a terminator build in. The smart ones sense the bus 1st, and only power the terminator when needed! That is why you can often not connect some drives internally Most intermittend problems are due to loose connectors, improper termination or inferior cable quality. The shorter the Cables the better. It basically does not matter what ID you assign to each device, as long as they are unique. It is good practice to number them in sequence as they are attached to the bus or to stick the common settings as follows.
Some sample configurations:


Normal assignation:

Device	Normal ID	Binary
Disk C:	0	0 0 0
Disk D:	1	0 0 1
Disk E:	2	0 1 0
Disk F:	3	0 1 1
Tape Drive	4	1 0 0
CD-ROM	5	1 0 1
Disk H:	6	1 1 0
Host Adapter (SCSI Controller)	7	1 1 1


The normal setup for the first controller (programmed mode) is: IO x330, IRQ 11 and DMA 5
Most devices support parity and are using synchronous transfer mode (rather than async, where every byte is acknowledged).
Some devices support LUN (Logical Unit Numbering). With this technique you can assign up-to 8 devices per SCSI ID. Thus the total possible devices comes to 56 per normal narrow SCSI Bus. This usually requires a controller in the cabinet where the CD-ROM's are mounted. Not all SCSI Controllers are LUN capable, however most are. Also the Software must be able to use LUN adressing. The most common use for LUN is a small SCSI CD-Changer (like the Pioneer DRM-604).

All distances in meters

STA Terms	Single-Ended	Differential	LVD (2)
SCSI-1	6	25	12
Fast SCSI	3	25	12
Fast Wide SCSI	3	25	12
Ultra SCSI	1.5-3	Up to 25	Up to 12
Wide Ultra SCSI	Up to 3	Up to 25	Up to 12
Ultra2 SCSI	(1)	(1)	12
Wide Ultra2 SCSI	(1)	(1)	12
Ultra3 SCSI	(1)	(1)	12
Wide Ultra3 SCSI	(1)	(1)	12
Ultra4 SCSI	(1)	(1)	12
Wide Ultra4 SCSI	(1)	(1)	12

LVD Cables for Point-to-Point Connections can be as long as 25m (83ft)
(1) Single-ended and high voltage differential are not defined at Ultra2, Ultra3 and Ultra4 speeds.
(2) Only if all devices on the bus support LVD.

STATerms	Bus speed (MHz)	Bus width (Bits)	Max bus length (meters)			Max devices (HA is also 1 device)
			Single ended	Differential	LVD
SCSI-1	5	8	6	25	12	8
Fast SCSI	10	8	3	25	12	8
Fast Wide SCSI	10	16	3	25	12	16
Ultra SCSI	20	8	1.5	25	12	8
Ultra SCSI	20	8	3	25	12	4
Wide Ultra SCSI	20	16	-	25	12	16
Wide Ultra SCSI	20	16	1.5	-	-	8
Wide Ultra SCSI	20	16	3	-	-	4
Ultra2 SCSI	40	8	(1)	(1)	12	8
Wide Ultra2 SCSI	40	16	(1)	(1)	12	16
Ultra3 SCSI	40	8	(1)	(1)	12	8
Wide Ultra3 SCSI	40	16	(1)	(1)	12	16
Ultra4 SCSI	80	8	(1)	(1)	12	8
Wide Ultra4 SCSI	80	16	(1)	(1)	12	16


(1) Single-ended and high voltage differential are not defined at Ultra-2, 3 and 4 speeds.

STA Term	Previously Known As
SCSI-1	SCSI-1 (X3.131-1986)
Fast SCSI	SCSI-2 (X3.131-1994)
Ultra SCSI	Fast 20, SCSI-3, Double-speed (SCSI)
Ultra2 SCSI	Fast 40, SCSI-3
Ultra3 SCSI	Fast 80, SCSI-4

50-Pin Connector Pinout

CONNECTOR CONTACT	SIGNAL NAME	CONNECTOR CONTACT	SIGNAL NAME
1	GROUND	26	TERMPWR
2	DB (0)	27	NC
3	GROUND	28	NC
4	DB (1)	29	GROUND
5	GROUND	30	GROUND
6	DB (2)	31	GROUND
7	GROUND	32	ATN
8	DB (3)	33	GROUND
9	GROUND	34	GROUND
10	DB (4)	35	GROUND
11	GROUND	36	BSY
12	DB (5)	37	GROUND
13	GROUND	38	ACK
14	DB (6)	39	GROUND
15	GROUND	40	RST
16	DB (7)	41	GROUND
17	GROUND	42	MSG
18	DB (P)	43	GROUND
19	GROUND	44	SEL
20	DB (0)	45	GROUND
21	GROUND	46	C/D
22	GROUND	47	GROUND
23	NC	48	REQ
24	NC	49	GROUND
25	NC	50	I/O

Signal Name	Pin Number	Pin Number	Signal Name
GROUND	1	35	-DB(12)
GROUND	2	36	-DB(13)
GROUND	3	37	-DB(14)
GROUND	4	38	-DB(15)
GROUND	5	39	-DB(P1)
GROUND	6	49	-DB(0)
GROUND	7	41	-DB(1)
GROUND	8	42	-DB(2)
GROUND	9	43	-DB(3)
GROUND	10	44	-DB(4)
GROUND	11	45	-DB(5)
GROUND	12	46	-DB(6)
GROUND	13	47	-DB(7)
GROUND	14	48	-DB(P)
GROUND	15	49	GROUND
GROUND	16	50	GROUND
TERMPWR	17	51	TERMPWR
TERMPWR	18	52	TERMPWR
RESERVED	19	53	RESERVED
GROUND	20	54	GROUND
GROUND	21	55	-ATN
GROUND	22	56	GROUND
GROUND	23	57	-BSY
GROUND	24	58	-ACK
GROUND	25	59	-RST
GROUND	26	60	-MSG
GROUND	27	61	-SEL
GROUND	28	62	-C/D
GROUND	29	63	-REQ
GROUND	30	64	--I/O
GROUND	31	65	-DB(8)
GROUND	32	66	-DB(9)
GROUND	33	67	-DB(10)
GROUND	34	68	-DB(11)

Note: The minus sign next to a signal indicates active-low.

CONNECTOR CONTACT	SIGNAL NAME	CONNECTOR CONTACT	SIGNAL NAME
1	+DB (12)	35	-DB (12)
2	+DB (13)	36	-DB (13)
3	+DB (14)	37	-DB (14)
4	+DB (15)	38	-DB (15)
5	+DB (P1)	39	-DB (P1)
6	Ground	40	Ground
7	+DB (0)	41	-DB (0)
8	+DB (1)	42	-DB (1)
9	+DB (2)	43	-DB (2)
10	+DB (3)	44	-DB (3)
11	+DB (4)	45	-DB (4)
12	+DB (5)	46	-DB (5)
13	+DB (6)	47	-DB (6)
14	+DB (7)	48	-DB (7)
15	+DB (P)	49	-DB (P)
16	DIFFSENS	50	DIFFSENS
17	TERMPWR	51	TERMPWR
18	TERMPWR (P)	52	TERMPWR
19	RESERVED	53	RESERVED
20	+ATN	54	-ATN
21	GROUND	55	GROUND
22	+BSY	56	-BSY
23	+ASK	57	-ASK
24	+RST	58	-RST
25	+MSG	59	-MSG
26	+SEL	60	-SEL
27	+C/D	61	-C/D
28	+REQ	62	-REQ
29	+I/O	63	I/O
30	GROUND	64	GROUND
31	DB (8)	65	-DB (8)
32	+DB (9)	66	-DB (9)
33	+DB (10)	67	-DB (10)
34	+DB (11)	68	-DB (11)

SCA and 68pin connectors have basially the same signals. In the SCA connector all 3 connectors (SCSI Bus, SCSI ID Selector, Power) normally found on a 68pin drive are combined into 1 single 80pin connector. There are adapters to convert 80 pin into the 3 seperate 68pin style connectors. They often also feature a 50 pin narrow connector and a terminator option. These SCA connectors are the most predominant connectors nowadays for pluggable (Hot Plug, Hot Swap) drives.

CONNECTOR CONTACT	SIGNAL NAME	CONNECTOR CONTACT	SIGNAL NAME
1	12 VOLT	41	12 volt GROUND
2	12 VOLT	42	12 volt GROUND
3	12 VOLT	43	12 volt GROUND
4	12 VOLT	44	12 volt GROUND
5	Reserved/NC	45	Reserved/NC
6	Reserved/NC	46	Reserved/NC
7	DB (11)	47	GROUND
8	DB (10)	48	GROUND
9	DB (9)	49	GROUND
10	DB (8)	50	GROUND
11	I/O	51	GROUND
12	REQ	52	GROUND
13	C/D	53	GROUND
14	SEL	54	GROUND
15	MSG	55	GROUND
16	RST	56	GROUND
17	ACK	57	GROUND
18	BSY	58	GROUND
19	ATN	59	GROUND
20	DB (PO)	60	GROUND
21	DB (7)	61	GROUND
22	DB (6)	62	GROUND
23	DB (5)	63	GROUND
24	DB (4)	64	GROUND
25	DB (3)	65	GROUND
26	DB (2)	66	GROUND
27	DB (1)	67	GROUND
28	DB (0)	68	GROUND
29	DB (P1)	69	GROUND
30	DB (15)	70	GROUND
31	DB (14)	71	GROUND
32	DB (13)	72	GROUND
33	DB (12)	73	GROUND
34	5 volt	74	5 volt GROUND
35	5 volt	75	5 volt GROUND
36	5 volt	76	5 volt GROUND
37	SYNC	77	ACTIVE LED OUT
38	RMT START	78	DLYD START
39	SCSI ID (0)	79	SCSI ID (1)
40	SCSI ID (2)	80	SCSI ID (3)

For a description of all the SCSI-Terms used, please refer to the Terms.

To see a list of many of the sites that link to this site, see here.
For further information about SCSI please contact the STA (SCSI Trade Association) or SCSI and other IO interfaces.

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