SCSI connectors

This Web page last updated Oct 6 2016. To email me or to order, see see my ordering Web page for my email addresses.

SCSI connectors on drives, cases, cables

This document is not guaranteed to be complete, accurate or correct. Look at other Web sites to get more information. It's simply a convenient reference for myself and my customers as a common source of information. I offer SCSI drives as part of my Apple Mac Web pages. I'd appreciate corrections. - Herb Johnson


Connectors are said to have "pins" but they may be either socketed contacts or pin contacts. Connectors with pins or plugs are often called "male", with sockets "female"; one fits into the other of like size and configuration. There are a variety of connectors for SCSI devices, because the connectors are associated with various versions or standards of SCSI interfaces, with different features and speeds of operation. But one often can use simple "adapters" (pairs of different connectors wired together) to convert from one connector type to another. But devices like "USB to SCSI" are not mere wired "adapters", they contain controller electronics and provide signal conversions; they may require software "drivers" on your computer.

"SCSI" is a set of standards for connecting and controlling devices, which have existed for decades. Versions are called "SCSI" or "SCSI-1" or "SCSI-2". Each supports different speeds of operation, how much data is read at once (8-bit, 16-bit), control features, number of allowed SCSI devices (addresses), etc. Despite these operational differences, you may be able to use "adapters" to physically connect older SCSI devices to newer computers. WARNING - "connecting" doesnt' mean "it will work" - you may need "drivers" for a specific device, plus software to actually use the device (as a scanner, camera, etc.).

This section has photos of drive connectors, cable connectors, and case connectors. A SCSI drive will be inside a case or computer, and connected by a cable to an external connector. Other cables are used to connect computers to external cabinets or other SCSI devices. These photos may include an inch ruler to give an idea of the size of these connectors: the photos are not to the same scale.


[connector] This image is the SCSI "female" connector for an external SCSI case. It's usually called a "Centronics 50-pin SCSI-1" connector; it's the oldest of SCSI connectors. It has two rows of 25 connections, and is 2-1/2" long. The mating connector looks similar in shape and size but the pins are on a "bump" so it's called a "male" connector. A matching male connector looks like this image, of a SCSI-1 terminator.

[connector] This image is the SCSI connector on the back of a typical older Mac computer. It's called a "DB-25" connector, and it has 25 pins arranged as two rows, of 12 and 13. WARNING: This connector is used in the PC/Windows world for "serial" or "parallel" interface devices, not necessarily SCSI. Serial or parallel cables with the mating DB-25 connector MAY NOT BE SUITABLE for SCSI work. WARNING II: IBM PC type SCSI DB-25 controllers or cables (rare) may not match Apple/Mac SCSI DB-25.

[connector] This image is the SCSI connector inside a computer or inside a SCSI external case. This connector is typical for "flat cables" for SCSI-1 type drives. Its a rectangular connector with two rows of 25 pins, 2-3/4" long. (NOte: IDE or ATA drive cables have a 40-socket connector.)

[connector] This image is the SCSI-2 connector for an external SCSI case. It's a narrow D-shaped "high density" connector 1-3/8" long, with 50 pins, two rows of 25. It's shorter than the similar-looking 68-pin SCSI-2 drive connector shown below.

[connector] This image is of connectors on the back of internal SCSI drives: a SCSI-2 drive (top) and a SCSI-1 (bottom) drive. The top connnector is a narrow D-shaped 68 socket SCSI-2 "high density" connector, 1-3/4" long. It's longer than the 50-pin SCSI-2 external connector shown above. The bottom connector is a rectangular 50-pin connector, 2-3/4" long, for SCSI-1 drives. (NOte: IDE or ATA drives have a 40-socket rectangular connector, 2-1/4" long.) Typically these connect to internal cables in computers or in external drive cases, with the mating cable connectors.

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Herb Johnson
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