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From: ardai@teda.Teradyne.COM (Mike Ardai)
Newsgroups: comp.sys.ibm.pc.hardware,comp.sys.laptops
Subject: Re: ADDING 3.5" DRIVE TO SHARP PC-5401 LAPTOP
Keywords: 3.5" pc-4501
Message-ID: <23454@teda.Teradyne.COM>
Date: 3 Apr 91 16:27:25 GMT
References: <1737@marlin.NOSC.MIL>
Followup-To: comp.sys.ibm.pc.hardware
Distribution: usa
Organization: Teradyne EDA, Inc.
Lines: 31

In article <1737@marlin.NOSC.MIL> farris@marlin.NOSC.MIL (Russell H. Farris) writes:
-
-      I added a Chinon 1.44mb disk drive to my single-drive Sharp
-PC-4501 laptop and now the computer behaves very strangely.
-
-      Either drive will work fine as A:, but neither will work
-correctly as B: (or C:, or D:, etc.).  CHKDSK works for B: and
-identifies it correctly as a 720k drive, but when I use DIR it
-says B: is "not ready." I can COPY to B:, but I can't DEL files
-from it.
-
-      I am using a flat 34-pin cable with pin 15 clipped out (as
-in the original Sharp cable).  Drive selection is by means of
-jumpers/switches.  I am using MSDOS 3.3 and have tried the
-following lines in my CONFIG.SYS file.

I have successfully added a 720k drive to a 4501.  In order to
'force' you to buy drives from Sharp, they have messed around
with the drive select scheme.  It has been a while since I did this,
but as far as I remember, one of the drives is selected by 
'drive select' and the other by 'motor enable'.  What I had to
do was to clip drive select on b and connect it to motor enable
on b (I think.  it may have been the other way around.)  Just 
probe around with an LED while doing 'dir a' and 'dir b' to see
what is really happening.
/mike

-- 
\|/  Michael L. Ardai   Teradyne EDA East
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