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Path: utzoo!watmath!clyde!cbosgd!ihnp4!wlcrjs!rhesmith
From: rhesmith@wlcrjs.UUCP (Richard H. E. Smith II)
Newsgroups: net.micro
Subject: Re: Erasing Disks
Message-ID: <635@wlcrjs.UUCP>
Date: Sat, 16-Mar-85 04:02:18 EST
Article-I.D.: wlcrjs.635
Posted: Sat Mar 16 04:02:18 1985
Date-Received: Sun, 17-Mar-85 01:05:27 EST
References: <1960@sdcc6.UUCP> <736@ihnp4.UUCP>
Reply-To: rhesmith@wlcrjs.UUCP (Richard H. E. Smith II)
Organization: chi-net, Public Access UN*X, Chicago IL
Lines: 51
Summary: Don't do it to DEC RX50 floppies

I'd better stick in my two cents here, or somebody is going to get worried...

In article <736@ihnp4.UUCP> cfiaime@ihnp4.UUCP (Jeff Williams) writes:
>
>> I had seen ads advertising a device to erase floppy disks much as a
>> tape eraser works on cassettes....
>
>It is funny that you mention this.  Last night I was talking with a DEC
>c.e. concerning floppy disks on a PDP 11/23+.  One of the comments that
>he made was that if a bulk eraser is used on a floppy for that system,
>servo (head) positioning data is lost on the floppy, and the disk is
>totally useless.  There is no field program to reformat that part of the
>disk, at least according to him.  I have no reason to doubt him.
>
>Of course, we were talking about one specific system, and one type of
>drive (the RX02).  These comments may not apply to a 5 1/4 inch drive
>on a PC, but do you want to experiment?
>
Here's the straight dope on DEC floppies:

There's no problem with the RX02 drive formatting disks, so you can bulk
erase them if you want.  It will format either single ("RX01 compatable")
or double density.  The RX02 is an 8-inch, single-sided drive.

The RD50 5-1/4-inch floppy drive (the one packaged in the micro-PDP-11)
cannot format its floppies.  If I understand correctly, and I'm pretty
sure I do, it's not missing format software, but actual missing hardware.
So if you erase the formatting, you're stuck unless you have a DEC RAINBOW
pc which uses the same disk format and CAN format disks.  For you hackers,
I don't think that you can do it on your [non-DEC] pc, since these are
96-tpi quad density (single sided) disks.

RX01 (old single density 8-inch floppy) might not be able to format,
either.  I can't remember anymore.  but you can get these formatted
just about anyplace that's 8-inch.

VT180 ("Robin"), I have no idea.

Why is it done this way?  Who knows... maybe to lock you into a disk
supplier (until others could make disks preformatted to this format, which
they now do, but it took a few months)... maybe just a cost reduction
on the controller.

Always glad to help.

-- 
==========
Dick Smith						..ihnp4!wlcrjs!rhesmith
==========
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