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Black Box Explains...SCSI-1, SCSI-2, SCSI-3, and SCSI-5

There are standards…and there are standards applied in real-world applications. This Black Box Explains illustrates how SCSI is interpreted by many SCSI manufacturers. Think of these as common SCSI connector types, not as firm SCSI specifications. Notice, for instance, there’s a SCSI-5, which isn’t listed among the other approved and proposed specifications. However, for advanced SCSI multiport applications, SCSI-5 is often the connector of choice.

SCSI-1
Supports transfer rates up to 5 MBps and seven SCSI devices on an 8-bit bus. The most common connector is the Centronics® 50 or a DB50. A Micro Ribbon 50 is also used for internal connections. SCSI-1 equipment, such as controllers, can also have Burndy 60 or 68 connectors.

SCSI-2
SCSI-2 introduced optional 16- and 32-bit buses called “Wide SCSI.“ Transfer rate is normally 10 MBps but SCSI-2 can go up to 40 MBps with Wide and Fast SCSI. SCSI-2 usually features a Micro D 50-pin connector with thumbclips. It’s also known as Mini 50 or Micro DB50. A Micro Ribbon 60 connector may also be used for internal connections.

SCSI-3
Found in many high-end systems, SCSI-3 commonly uses a Micro D 68-pin connector with thumbscrews. It’s also known as Mini 68. The most common bus width is 16 bits with transfer rates of 20 MBps.

SCSI-5
SCSI-5 is also called a Very High-Density Connector Interface (VHDCI) or 0.8-mm connector. It’s similar to the SCSI-3 MD68 connector in that it has 68 pins, but it has a much smaller footprint. SCSI-5 is designed for SCSI-5, next-generation SCSI connections. Manufacturers are integrating this 0.8-mm design into controller cards. It’s also the connector of choice for advanced SCSI multiport applications. Up to four channels can be accommodated in one card slot. Connections are easier where space is limited.