Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!hellgate.utah.edu!helios.ee.lbl.gov!ucsd!ucsdhub!hp-sdd!hplabs!hpda!hpcuhb!hp-ses!hpdml93!stephen
From: stephen@hpdml93.HP.COM (Stephen Holmstead)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Apple SCSI not compatible with standard SCSI?
Message-ID: <15450003@hpdml93.HP.COM>
Date: 29 Nov 89 16:15:06 GMT
References: <24105@cup.portal.com>
Organization: Hewlett Packard - Boise, ID
Lines: 29

dawill@hubcap.clemson.edu (david williams) writes:
>     Hummm.  I am in the process of hacking together a 50pin-to-25pin connector
>for a StarDrive I recently got.  The target drive (my roomate's) is a miniscribe
>8425S.  Is this drive differential?  If not, how often is differential drive
>used in the REAL world?  I have a feeling that this would only be used on 
>really high-end drives, much as professional audio uses balanced connectors, and
>consumer stuff only uses single-ended.

Yup.  Differential drives are mostly used on high-end systems.  The SCSI
bus uses +12V and -12V signal levels as opposed to +5v and GND used on
Single-ended drives.  Obviously, the differential drives are not as
sensitive to say a 2V signal drop as would a single-ended drive.

NOTE TO EVERYONE WHO IS WORRIED IF THEY HAVE A DIFFERENTIAL DRIVE ON
THEIR AMIGA:  All of the SCSI controllers that I know of for the Amiga
use single-ended SCSI.  You would *REALLY* know if you put a differential
drive on a single-ended controller!! :-)

I would *LOVE* to see standardization of cables (eg, SCSI means 50 pin
cable, serial interface means DB-25 cable, etc.).  Speaking of standard
cables, what possessed Commodore to use a DB-23?!?!?!? :-)

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Stephen Holmstead
...!hplabs!hpdmlge!stephen                      //
Hewlett Packard Disk Memory Division          \X/  Amiga Forever!

"I remind you that humans are only a tiny minority in this galaxy."
	-- Spock, "The Apple," stardate 3715.6.