SCSI connector

A SCSI (Small Computer System Interface) connector is a physical interface used to connect internal and external peripherals to a computer system. It serves as the gateway for the high-speed parallel SCSI bus, which allows for the daisy-chaining of multiple devices—such as hard drives, tape drives, scanners, and optical drives—from a single controller.

Key Characteristics:

1. Variety and Evolution: Unlike many standardized connectors, SPIU (SCSI Parallel Interface) connectors evolved significantly across various SCSI standards (SCSI-1, SCSI-2, Ultra SCSI, etc.). This resulted in a wide array of connector types, differing in pin count, size, and configuration.

2. Common Types:

   • Internal Ribbon (IDC) Connectors: Typically a 50-pin (Single-Ended/Narrow) or 68-pin (Differential/Wide) header on the device, designed to connect to a flat ribbon cable.

   • External High-Density (HD) Connectors:

     • DB-25: A 25-pin D-subminiature connector (similar to a parallel port), common on older Apple Macintosh and SCSI-1 devices.

     • Centronics 50-pin: A bulky connector with a wire clip latch, used primarily on early external SCSI devices like scanners and printers.

     • High-Density 50-pin (HD-50): A smaller, denser alternative to the Centronics connector.

     • High-Density 68-pin (HD-68): The most common external connector for Wide SCSI, Ultra SCSI, and later standards. It is a robust, rectangular connector with a screw-lock mechanism for secure attachment.

3. Daisy-Chaining: A defining feature of SCSI is its ability to connect multiple devices in a series on a single bus. This requires proper termination at both physical ends of the bus to prevent signal reflection and errors.

4. Legacy Status: While once the premier standard for high-performance workstations and servers, parallel SCSI and its connectors have been largely superseded by serial interfaces like SAS (Serial Attached SCSI), SATA, and USB, which offer simpler cabling, higher speeds, and easier configuration.