SCSI Connectors FAQ, HD, DB, SCA, VHDCI, offset

SCSI Connectors FAQ
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SCSI Connector Name	Click to see picture	Number of pins	Number of rows	Width at widest point	Wide or Narrow?	Standard Hardware?	Pins or Contacts	Rare?
High Density 68 pin (aka HPDB68)	HD-68	68	2	1.87"	Wide	Thumb screws	pins	common
High Density 50 pin (aka HPDB50)	HD-50	50	2	1.43"	Narrow	Spring Clips	pins	common
Centronics 50 pin	CX-50	50	2	2.5"	Narrow	Wire Clip	contacts	common
D Sub 25 pin	DB-25	25	2	1.56"	Narrow	Thumb screws	pins	common
D Sub 50 pin (often confused with HD-50)	DB-50	50	3	2.12"	Narrow	Thumb screws	pins	rare
Very High Density Centronics Interface 68 pin .8mm	VHDCI-68	68	2	1.31"	Wide	Thumb screws	contacts	common
Offset Very High Density Centronics Interface 68 pin .8mm	Offset VHDCI-68	68	2	1.31"	Wide	Thumb screws	contacts	common
High density 68 pin mini Centronics 68 pin RS6000	Mini CX-68	68	2	*	*	*	contacts	very rare
High density 60 pin mini Centronics 60 pin RS6000	Mini CX-60	60	2	*	Narrow	*	contacts	rare
High density 50 pin mini Centronics 50 pin	Mini CX-50	50	2	*	Narrow	*	contacts	rare
High density 80 pin micro Centronics 80 pin SCA (Single Connector Attachment)	MCX-80 SCA	80	2	2.18"	Wide	none / guide	contacts	common

* unknown or not available at this time.

SCSI Connectors FAQ

What connectors are available?
What does centronics or CX mean?
What is HD?
What is IDC?
What is MCX?
What is DB?

What does centronics or CX mean?

Centronics is a style of connector which uses "plates" instead of "pins". You will never find actual pins on a centronics style connector.

"The "Centronics" connector gets its name today from the fact that the 36-pin connector was first used on the Centronics printer, a popular, low-cost dot-matrix printer first offered back in the sixties." - Walt Foley

What is HD?

HD stands for "High Density". High density scsi connectors are typically "D" shaped and only have 2 rows. The only exception is the HDI-30, which is 5 rows and square. The most common external SCSI connectors today are HD-50 and HD-68. The HD-50 connector usually uses clips and is called SCSI-2 by many hardware vendors. The HD-68 connector usually uses screws and is called SCSI-3 by many hardware vendors. The HDI-30 does not use screws or clips, and it is commonly used with PowerBooks.

What is IDC?

IDC is a term that refers to square internal connectors, usually connected to ribbon cables. They are usually black with no hardware. Some of these connectors have keys or knockouts. The IDC 50 is the connector most commonly used with older SCSI devices. As a side note, IDC 40 connectors are used with IDE drives, and IDC 34 connectors are used with 3 1/2" floppy drives.

What is MCX?

MCX stands for "Micro-centronics". Micro-centronics connectors are found on SCA drives and some newer high-end SCSI devices and controllers. MCX 80 is commonly referred to as SCA. SCA is short for "single connector attachment" and is being implemented by many hardware manufacturers today. The VHDCI 68 (aka SCSI-5) connector is an MCX style connector. Mini CX 50, 60, and 68 are commonly referred to as "RS6000" connectors, because they were used by IBM in RISC 6000 systems way back when. Caution is needed here when looking for MCX 68 cables. When a vendor uses the term MCX 68 without RS6000, VHDCI, .8mm, or .5, you need to ask more questions.

What is DB?

DB is the most common style of connector used on computer systems today. Serial, parallel, and SCSI all use DB style connectors. SCSI uses the DB-25 and DB-50 (very rare) connector. A DB connector is "D" shaped and typically uses 2 rows of large pins. The DB-50 is an exception, because it uses 3 rows. Be careful when dealing with DB-25 ports. A parallel port and a SCSI port look the same on some computers. (Past experience has shown that plugging a parallel printer into a SCSI port causes damage to all of the devices on the channel, including internal devices.)