Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!ames!sun-barr!newstop!sun!imagen!atari!portal!cup.portal.com!Sullivan
From: Sullivan@cup.portal.com (sullivan - segall)
Newsgroups: comp.sys.amiga
Subject: Re: fixing a 3.5" drive
Message-ID: <19377@cup.portal.com>
Date: 11 Jun 89 22:11:46 GMT
References: <206@tlvx.UUCP>
Distribution: usa
Organization: The Portal System (TM)
Lines: 58

>Recently, someone plugged in a bad external drive into my A1000, which shorted
>out the 8520 and floppy drive (apparently).  After swapping with a good
>(borrowed) 8520, my A1000 gets the kickstart screen, but the drive doesn't work.
>Since then, it's been a struggle to find an 8520 and replacement drive.  I don't
>have the 8520 yet, but I did purchase an IBM-type 720K 3.5" drive (made by
>Toshiba).  It looks like it'll work (although the mounting is different [I don't
>mind drilling holes], the connectors and cables are all the same, except for the
>LED for "drive busy").  Is there something I need to know (perhaps jumper
>settings needed, such as the DC/RDY jumper)?  Is this going to work?  (Unless
>someone says, "No way!" I'm goin' for it as soon as I get the 8520.)

It's been a while, so this explanation is only to get you on the right
track.  I have an 80track IBM 3.5" floppy in my Amiga.  It has some limitations:
 Since the drive doesn't correctly identify itself when the Amiga resets it, 
Some programs will not work correctly.  The only program that I've encountered
so far that continuously resets the floppy drive is the public domain copier
NIB v1.0.  Marauder also displays odd behaviour if a diskette is in the drive
when a copy is first requested.  Also when rebooting, the drive must identify
itself so that the Amiga will recognize it and configure correctly.  Since the
floppy drives are supposed to respond with $FFFF,FFFF on the diskready line
you can simulate this behaviour by popping any floppy disks out of the drive,
which will drive the disk ready line high (disk not ready.)  If you do not 
remove the diskette before rebooting the drive will be deconfigured.  (It will
be as though it were not attached.  Keep these limitations in mind before you 
decide to use a non-Amiga floppy drive.

With that in mind, the floppy cable in the Amiga is keyed backwards from those
on PC's.  To attach the drive you will have to file down the plastic key on the
ribbon cable connector, and attach it upside down.  The drive select should be
set to the first drive (drive 0 for older floppies, drive 1 if that is the 
lowest.)  As I recall, the addresses of the drives are selected by a twist in 
the ribbon cable, and so you shouldn't need to change the drive select however
many drives you are using.  
>
>I was seriously tempted to get a 1.44 meg floppy and see if I could make a
>mountlist entry to store 1.44 megs (perhaps in FFS format).  I decided to take
>the safest route possible, and to not deal with this complication.  I would
>be interested in hearing if it's possible or not....
>
>-- 

The amiga diskcontroller hardware is not capable of reading bits at the 
rate required for a 1.44 meg floppy.

>Gary Wolfe  usenet: ..uunet!mimsy!ames!mailrus!uflorida!unf7!tlvx!sysop
>            BBS   : SysOp of The Temporal Vortex BBS at 904-771-8589


                           -Sullivan Segall
_________________________________________________________________

/V\  Sullivan  was the first to learn how to jump  without moving.
 '   Is it not proper that the student should surpass the teacher?
To Quote the immortal Socrates: "I drank what?" -Sullivan
_________________________________________________________________

Mail to: ...sun!portal!cup.portal.com!Sullivan or
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