Took this from RAM Electronics at in May 2004. It's a good reference, and my observation has been that over time things disappear from the web. In the mean time if they're still there, go buy something from them.

SCSI Connectors
and SCSI Cable information
SCSI Terms, SCSI specifications - SCSI cable length specs

The Connectors:

 50 Pin Header
IDC50 Female

idc50 male connector
IDC50 Male

IDC 50 pin female, mates to IDC50 male "header", used on SCSI-1, SCSI-2, Ultra SCSI "narrow" etc. All internal 50-conductor "8-bit" SCSI uses these cconnectors.

Centronics 50
CN50 Male
cn50 female scsi connector
CN50 Female

Centronics C50  sometimes referred to as CN50, Cent50  (External connector on many SCSI-1 and some SCSI-2 Controllers) The controller connector and peripherals connectors should be females, and the cables male.


DB25 male scsi connector
DB25 Male
Used with the older Macs, Zip drives, and many scanners.

db25 female scsi connector
DB25 Female

hd50 male scsi connector
HD50 Male
Mini D50 “HPDB50” (SCSI-2/SCSI-3 external connector) . The easy way to tell the difference between an HD50 and an HD68 (unless you want to count those tiny little pins) is to measure them. HPDB50 is about 1 3/8” (36mm) , and the HPDB68 is about 1 7/8” (47mm)

hd50 female scsi connector
HD50 Female

hd68 male scsi connector
HD68 Male
MiniD68 “HPDB68” (Ultra wide SCSI-3/ Ultra2 LVD SCSI/ wide Differential SCSI both internal and external) The internal and external connectors appear to be different, but they are the same basic connector. The easy way to tell the difference between an HD50 and an HD68 (unless you want to count those tiny little pins) is to measure them. HD50 is about 1 3/8” (36mm) , and the HD68 is about 1 7/8” (47mm).

hd68 female scsi connector
HD68 Female
vhdci male scsi connector
VHDCI male
VHDCI 0.8mm HPCN68 male- Sometimes called SCSI-5. Very popular in RAID cards.
VHDCI female scsi connector
VHDCI female

HDI-30 scsi connector

HDI-30 is for Apple Macintosh PowerBooks.  

Used in Japan, on several Digital cameras and things.

HPCN50 pin (rare)


DB50 Male
Usually used on old Sun Sparcstations.
DB50 Female



Female DB37

Mini Centronics 60

Mini Centronics 60 “HDCN60”  (old IBM RS6000)
We don't carry these cables anymore 

The SCSI Types Bus lengths, devices supported, etc.
Much more info on SCSI Cable lengths and "gotchas" below the chart
STA (SCSI Trade Association) -Endorsed Terms & Terminology for SCSI Parallel Interface Technology.
see here for term descriptions

STA Terms
(notes-see below)

Bus Speed, MBytes/Sec. Max. Bus Width, bits  

Max. Bus Lengths, Meters (1)

Max. Device Support
Single- ended LVD HVD
SCSI-1(2) 5 8 6 (3) 25 8
Fast SCSI (2) 10 8 3 (3) 25 8
Fast Wide SCSI 20 16 3 (3) 25 16
Ultra SCSI (2) 20 8 1.5 (3) 25 8
Ultra SCSI (2) 20 8 3 - - 4
Wide Ultra SCSI 40 16 - (3) 25 16
Wide Ultra SCSI 40 16 1.5 - - 8
Wide Ultra SCSI 40 16 3 - - 4
Ultra2 SCSI (2,4) 40 8 (4) 12 25 8
Wide Ultra2 SCSI (4) 80 16 (4) 12 25 16
Ultra3 SCSI or Ultra160 SCSI (6) 160 16 (4) 12 (5) 16
Ultra320 SCSI (6) 320 16 (4) 12 (5) 16

(1) The listed maximum bus lengths may be exceeded in Point-to-Point and engineered applications.
(2) Use of the word "Narrow", preceding SCSI, Ultra SCSI, or Ultra2 SCSI is optional.
(3) LVD was not defined in the original SCSI standards for this speed. If all devices on the bus support LVD, then 12-meters operation is possible at this speed. However, if any device on the bus is singled-ended only, then the entire bus switches to single-ended mode and the distances in the single-ended column apply.
(4) Single-ended is not defined for speeds beyond Ultra.
(5) HVD (Differential) is not defined for speeds beyond Ultra2.
(6) After Ultra2 all new speeds are wide only.

The Cable Length Rules*

(In case you're not confused yet)
A short simplified guide to scsi cable lengths.

Type of SCSI

"Single-ended" (Regular) SCSI bus length

"Differential" SCSI bus length

LVD SCSI  bus length ††

5 MHz (SCSI-1)

 6 meters

25 meters


10 MHz (SCSI-2 FAST, Fast / Wide SCSI)

3 meters

25 meters


20 MHz (Ultra SCSI,  Ultra Wide SCSI or  "Fast20")

3 meters (3 devices + host adapter) or 1.5 meters (4 devices + host adapter)*

25 meters


40 MHz (Ultra2 SCSI or  "Fast40")



12 meters

*please note: "Ultra" SCSI cable lengths are severely limited! The maximum cable length is ten feet when four devices (including the host adapter) or less are on the bus. If five devices are used (four devices and your host adapter), then the maximum bus length is 1.5 meters (five feet!). ††Knocking Ultra2 or U160 chains out of LVD mode by putting "Legacy" Single Ended (regular Ultra scsi, etc) devices on the chain will give you the same cable length restrictions as Ultra scsi. Watch it!!

Note: Remember, the "bus" is the entire cable chain! This is not some kind of "each cable" can be this length kind of deal. Bear in mind that you need to use good quality cable and active termination to acheive even these results! There are some specs that are mostly related to internal cables, for example, the SCSI-2 specs state that there should be 12" of cable between connectors. This spacing however, is not always possible, depending on the number of connectors. Another limit to be aware of is the "stub length" (sort of like the length from the cable "bus" to the device) is limited to 4", so don't chain adapters together if you can help it and never think you can do some kind of "Y" cable setup! Another possible enhancement involves using different spacing between the connectors to limit reflective resonance. There's some debate about whether this does, in fact, have any benefits. You can get extremely carried away with making "the perfect" cable, but you will generally pay far more than you get back. So, basically, remember that excess cable length is a bad thing, and if it works, and works reliably, it's just fine, even if it bends a rule or two.

SCSI Products:
•SCSI Adapters (connector adapters)
•SCSI Terminators (Both SE and LVD)
•Differential Converters (HVD to LVD/SE)
SCSI External Cables (outside computer)
•SCSI Internal Cables (inside computer)
•SCSI Cards (controller cards)
•SCSI Ultra2/Ultra160 LVD cables
•SCSI Gender Changers  (M-M, F-F)
•SCSI Boosters (exend your SCSI length)
•SCSI Switches (2x1, 2x2 and 6x4)
•SCSI Switching Software
•SCSI "Powerswitch" Failover Clustering Solution
SCSI Bus Extenders: (lengths up to 10K)
•Powerlink (Uses Coax or fiber) •Lazerlink (Fiber)

SCSI Information:
SCSI connector pictures
The basics of SCSI for newbies and technical information

SCSI connection FAQ

SCSI cable Length guide

Need more info? Check out the T10 Home page, brought to you by LSI Logic Corp.
Also excellent is the SCSI Trade Associations home page.
There are even more links available from RAM Electronic's help page.