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Guide to the 50pin vs 25pin SCSI Interfaces

The most common cause of item return / exchange from our customers is caused by
confusion as to which SCSI interface is needed for a particular model of server
or workstation.

This article addresses INTERNAL interfaces only. Please see our article on
external interfaces if you are looking for an external device. There are four
internal interface types: 80pin, 68pin, 50pin and 25pin.

We will discuss 50 pin and 25 pin SCSI interfaces in this article.

The 50pin SCSI interface (8 bit) was widely used in desktop computers until
about 1996. It is limited to Narrow/Fast SCSI II which has a limit of just 10MB/s.
Examples of 50pin SCSI are often found in Apple SE, SE30; II, IIx, IIci, IIsi,
IIvi, IIvx; Apple Performa, LC I, II, III, 400, 405, 430, 450, 460, 475, 600,
611x Series; Apple Centris 610, 650, 660av, Apple Quadra 605, 610, 650, 660av,
700, 800, 840av, 900, 950, Apple PowerMac 6100, 7100 8100, 6400, 6500, 7200,
7300, 7500, 7600, 8500, 8600, 9500, 9600, G3 , PowerComputing computers, All
Umax workstations, & Most Motorola StarMax and StarMax based Mac clone computers,
older PCs with SCSI support, most older SCSI CD-ROM and internal tape drives.
Currently 50pin devices are no longer manufactured, however we sell 80-50pin
and 68-50pin SCSI adapters
, such that you can buy any of our of SCSI products
and an appropriate adapter to use them in your system.

The 25pin SCSI interface (8 bit) is the original SCSI interface and is truly
outdated. However many Apple computers continued to use the 25pin external interface.
For internal purposes you should really consider upgrading the SCSI controller
in your system, since it is very difficult to find 25pin devices or adapters
for this purpose.