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Old 20 April 2019, 02:17   #4
Monochrome and 8 bit

Join Date: Nov 2004
Location: Underbarrow, Gods Country
Age: 53
Posts: 598
OK, minor point to get out of the way: nothing uses SCSI-1 it has been dead since about 198something.

The 50pin SCSI connector is -strictly speaking - the best quality interface to use; all 50 pins are connected, including ground. Apple introduced a 25pin connector, which ties all the grounds to a single pin. Not a great idea. In the real world it doesn't make any difference until you have a problem, then it is a sod to diagnose as you can't rule the cable/connector out.

50-25 pin adaptors, or more commonly cables, are plentiful. Using one will not affect your throughput (or 'speed'). Unless the cable is at fault; then generally it will either not work, or you will see issues with devices not appearing, or hanging when read/written to.

The number of pins does not identify the SCSI version. E.g.

SCSI-1 and 2 use a 50pin connector. Fast-Wide SCSI-2 used two cables...

SCSI-1 and 2 use a 'narrow' bus - 8bytes but...a 68pin connector does not mean SCSI-3; the SCSI-2 Ultra-Wide interface uses a 68pin interface (16bit, 40Mhz).

The Fastlane uses a SCSI-2 8bit bus @ 10MHz, it is a not a SCSI-1 interface. With the correct cable (Centronics 50 to DB25?) you should have no problems.

Can't identify if the cable is good? It should be quite thick. If it is thin, then only 1 pin is being taken from the C50 port as ground. A thick cable will run all ground pins to a single pin on the DB25 end, which whilst not ideal, makes for a better cable.
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