3 1/2" on the 7300 (Reposting of original)

[Lenny Tropiano]

In article <1944 at uhccux.uhcc.hawaii.edu> richard at uhccux.UUCP (Richard Foulk) writes:
|>}If he doubled the amount of cylinders as in says in his article (see above
|>}quoted section) that means you will get double the space... about 720K.
|>}
|>}-Lenny
|>}
|>}BTW: You have to realize that 3.5" disks cost about twice as much as 5.25"
|>}     ones... so you'll get twice the space at twice the costs... One wonders
|>}     how much savings that is.. (Other than you sanity for inserting and
|>}     removing disks) 
|>
|>Reducing the pain of backing the system up is what it's all about.
|>I'm still waiting for an affordable tape system.  But a simple
|>doubling of diskette capacity is real tempting.
|>
|>Also, I think 3.5" disks have been found to be more reliable.
|>
|>Some time back someone posted an article about having installed a
|>3.5" drive on their unixpc and explained all about, including the
|>configuration files.  Perhaps someone could pull it out of the
|>archives and repost it.
|>
|>Richard

Here's the article that started this whole discussion... there weren't
any configuration files, but it should be as easy as:

#sccs	"@(#)iv:fdfmt-mini.nl	1.1"

iv -i /dev/rfp020 /usr/lib/iv/FDnl-mini
mkfs /dev/fp021
dismount -f > /dev/null 2>&1

---
/usr/lib/iv/FDnl-mini:

#sccs	"@(#)iv/lib:FDnl-mini	1.1"
type		FD
name		Floppy
cylinders	80
heads		2
sectors		8
steprate	0
singledensity
$
$
$
0
1
$
$

--

Original article follows:

|Article 2802 of comp.sys.att:
|Path: icus!mtune!codas!peora!ge-dab!ge-rtp!edison!toylnd!dca
|>From: dca at toylnd.UUCP (David C. Albrecht)
|Newsgroups: comp.sys.att
|Subject: 3 1/2" on the 7300
|Message-ID: <213 at toylnd.UUCP>
|Date: 28 May 88 03:01:07 GMT
|Distribution: na
|Organization: Dave & Anne in Charlottesville, VA
|Lines: 45
|
|Being an inveterate hacker, I've been at it again.  I wondered if the 7300
|could take a 3 1/2" drive since it would make backing up somewhat more
|pleasant and I already use an Amiga so have a supply of the little suckers
|on hand.  They do seem to cost more per MB unfortunately.  Therefore, when
|I saw the sale that good 'ol Radio Shack had on an external 31/2" drive for
|their 1000HX system (for $99, it should still be on), I sprang into action
|and got one.
|
|The cable coming out of the thing appeared useless.  Prying
|it apart the drive instide has a connector on the drive which is the same as
|the one coming off the 7300 motherboard.  It has a power connector which is a
|different size than the one on the 5 1/4 inside the 7300 but same stuff
|5v, 12v, 2 GNDs.  Inside the 3 1/2 drive box there is a pc board which
|converts the cable from the drive and power lines to go out the cable
|from the box.  I clipped the ribbon cable off at the pc board and stuck a 34
|pin connector on it (again from radio shack).  Then, I clipped the power lines
|at the pc board in preparation for an alligator to 5 1/4" power line connection
|job.  I then dug the 7300 I have for spare parts out of the box its in
|(I'm not crazy enough to do this on the 3b1 I use all the time).  Unplugged the
|5 1/4" from the motherboard and plugged in the 3 1/2".  Alligatored in the
|appropriate power lines and tried it.  No smoke but it didn't work.  Noticing
|that the 5 1/4" was selected to D0 while the 3 1/2" was D1, I changed it.
|Voila! It formatted.
|
|Stress test time.  Formatted it like a 5 1/4", no problem.  Copied an FD entry
|from /usr/lib/iv and doubled the number of cylinders, formatted again no
|problem.  Mounted it and copied files till it was full, then tried to use some
|of the last copied files, no problem.  Tried formatting a disk with 10
|sectors/cyl ala. some of the 5 1/4" distribution disks, uh uh, no good, hangs
|in formatting.  Oh well, I guess you can't have everything.  Don't know if you
|can format it as a 720K MSDOS disk.
|
|Just thought maybe some other people might be
|interested in this feasibility study.  Now I'm going to have to figure
|out how to hook it up so I can switch between the 5 1/4 and the 3 1/2
|(visions of 36 pin centronics switch boxes dancing in my head).  Getting the
|distribution disks on 31/2s could be challenging.  Ah well, future food for
|thought.
|
|Warning.  This project is not recommended for those not well versed in the ins
|and outs of cabling and the insides of PCs.  I will certainly not be held
|responsible for you mucking around inside your 7300/3b1.
|
|
|David Albrecht
|
-- 
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