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From: stephen@hpdml93.HP.COM (Stephen Holmstead)
Newsgroups: comp.sys.amiga.tech
Subject: Re: RS232 gender (was Re: Apple SCSI not compatible with standard SCSI?)
Message-ID: <15450005@hpdml93.HP.COM>
Date: 7 Dec 89 19:45:14 GMT
References: <503@shodha.dec.com>
Organization: Hewlett Packard - Boise, ID
Lines: 22

Keith Hanlan writes:
>What is meant by "differential SCSI"?
>What is meant by "single-ended SCSI"?

These are two options on types of signals on the SCSI bus.  Single-ended
SCSI signals change between +5v and GND, whereas differential SCSI
signals change between +12v and -12v.  Thus, on single-ended SCSI, half
of the pins are grounds, whereas they are -12v returns in differential
SCSI.

Q: Why do we have single-ended and differential options?
A: To confuse people. :-)
A2: Because differential SCSI, although more expensive, can have longer
cables and faster data rates.  Some people can't get by with the 6 meter
cable limit on single-ended SCSI. 1/2 :-)  (This doesn't really apply to
personal computers, but it does make sense if you think about a computer
lab environment with BIG computers).

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Stephen Holmstead                Hewlett Packard Disk Mechanism Division
...!hplabs!hpdmlge!stephen                      //
stephen@hpdmlge.boi.hp.com                    \X/  Amiga Forever!