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From: phs172m@vaxc.cc.monash.edu.au (Stephen Harker)
Newsgroups: comp.sys.apple2
Subject: Re: Re- Much about Quantums and
Message-ID: <1991Mar16.111704.86455@vaxc.cc.monash.edu.au>
Date: 16 Mar 91 01:17:04 GMT
References: <9103150330.AA02173@apple.com>
Lines: 39

In article <9103150330.AA02173@apple.com>, Joe_Luzzi.FULLERTON_CC@QMBRIDGE.CALSTATE.EDU (Joe Luzzi) writes:
> [a lot deleted]
> 
> I don't know why the quantum didn't work.  I have a Rodime 140 Plus hooked up
> to my Apple DMA SCSI card now and it works fine.  The Rodime has an external
> terminator and the SCSI cable is about 3-4 feet long.  I then wanted more disk
> space and ordered the Protege Quantum from MacAvenue.  I remove the terminator
> from the Rodime and connected up the Protege drive using a peripheral cable
> from Apple that's about 4 feet long.  The Protege drive would not work all
> alone on the chain (computer to Protege only).
> 
> So, that's the story.  I'm gonna try another Quantum from some other hard drive
> company or maybe just get a Chinook drive (Connor based mechanism).
 
	One last comment, from previous reading of comp.periphs.scsi and past
posts on this group (especially one crossposted by Thad Floryan in 1979) a lot
of SCSI drives don't (or didn't) have their internal wiring correct.  SCSI
devices are supposed to be daisy chained. However a lot are not internally
daisy chained.  So you could have a what you think is a daisy chained setup
(looking externally) but it is not.

SCSI drives are supposed to		Not like
look like

	[]--|	  |--[]				[]-----[]
	    |	  |					|
	    |	  |					|
	    |_____|					|
	       |					|
	       =					=

	Where [] represents the external 50 pin connectors and = represents the 
internal drive.  Apparently if this is not correct there can be vastly
increased noise in the system which can cause problems with daisy chained
drives.

-- 
Stephen Harker				phs172m@vaxc.cc.monash.edu.au
Monash University