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The Ten Commandments of SCSI

Copyright© Gary Field, 1994-2002 - All rights reserved.
Author: Gary Field - SCSI hacker since 1985
It is part of SCSI FAQ.
Last Updated: May, 2002


I . Thou shalt terminate both ends (and ONLY the ends) of thine SCSI bus. If thine bus is WIDE, be sure that both the lower half and upper half of the bus are properly terminated.


II. Thou shalt use active (or LVD/SE) terminators wherever possible.


III. Thou shalt make certain that each SCSI device has a SCSI ID unique unto itself.


IV. Thou shalt make certain that terminator power is supplied by at least one device (laptop users pay special heed!)


V. Thou shalt not make thine SCSI bus longer than the speed of thy fastest device allows. These being:


6 meters for 5 MHz (SCSI-1 synch)


3 meters for 10 MHz (SCSI-2 Fast)


1.5 meters for 20 MHz (Fast-20/Ultra)


12 meters for 40 MHz (Fast-40/Ultra2) or higher using LVD.


VI. Thou shalt not mix the tribes of SCSI! HVD cannot abide SE or LVD and neither can they abide HVD. Be sure you know which tribe each of your devices is from. HVD is now considered to be in exile and should be shunned if sighted in your vicinity.


VII. Thou shalt keep thine device drivers up to date (But keep a known working version around too).


VIII. Thou shalt make certain that the power supplies for your devices are adequate to supply their needs (even during peak usage).


IX. Thou shalt not worship false connectors. A special place in SCSI Hell is reserved for designers using 25 pin connectors on SCSI devices!


X.  Thou shalt double check that thou hast obeyed all of the above before posting a question to the enlightened in the comp.periphs.scsi newsgroup!