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From: scott@pita.cns.ucla.edu (Scott Burris)
Newsgroups: comp.os.386bsd.questions,comp.periphs.scsi,comp.sys.ibm.pc.hardware.cd-rom
Subject: Pioneer 604X CD changer questions and experience
Date: 13 May 1994 18:54:47 GMT
Organization: UCLA Campus Network Services
Lines: 26
Message-ID: <2r0ido$9mt@news.mic.ucla.edu>
NNTP-Posting-Host: pita.cns.ucla.edu


I just got a new 604X CD changer and I'm using it mainly under FreeBSD 1.1.
First off, it seems to have arrived without the instruction manual.
While my vendor tries to decide what to do short of exchanging the
drive (mail order, but the drive works, so I don't want to send it back), does
anyone have info on the dip switches in the back?  I found out that switch
4 sets SCSI-1 v.s. SCSI-2, but don't know what the others do.  Or do you
have a phone for the part of Pioneer which acknowledges that they make
CD-ROM drives (of course if I had my manual, I'd have a phone number :-(  )

Anyway, I'd like to solicit some thoughts on how to use this drive under
FreeBSD.  Under DOS or System 7, it takes some work to make the drive
thrash.  But under BSD, with all 6 disks mounted as filesystems, and no
reasonable way to serialize access, what's the best way to minimize thrashing?
Would the buffer cache be good enough?  Should I modify the CD-ROM driver
to use a private cache area?  What about putting a hack into the driver
so that an access of a LUN not already mounted blocks until the last LUN
switch has aged for a certain number of seconds?  Anyone have some 
real life experience to share?


-- 
----------
Scott Burris
UCLA Campus Network Services
cnetslb@oac.ucla.edu (310) 206-4860 - OR - scott@pita.cns.ucla.edu