info-cpm (12/10/82)
>From dag@UCBARPA.BERKELEY.ARPA Fri Dec 10 14:10:32 1982
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To: info-cpm@BRL, info-micro@BRL
Via: Ucb-C70; 10 Dec 82 5:55-EST
Via: Brl; 10 Dec 82 6:06-EST
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This comes third hand from a materials scientist in Silicon Valley
who is working on hard disk recording methods.
I am not sure of the actual techical accuracy, but the gist is
AVOID ELEPHANT MEMORY DISKS - THEY WILL SCREW UP
YOUR HEADS.
The disks have a large amount of what I think he called Alumina. Although
the disks do not seem to have many errors, they have an interesting side
effect. The alumina(?) is used to reduce cost and increase disk
reliability, but too much will erode the heads of disk drives.
The Elephant disks have too much.
I am trying to get a more specific and accurate description of
the problem and will post it as soon as I decipher it.
In the intevening weeks, simply beware of Elephehant memory disks.
Davidinfo-cpm (12/15/82)
>From POURNE@Mit-Mc Sun Dec 12 23:39:59 1982
To: dag@UCBARPA.BERKELEY.ARPA
Cc: info-cpm@BRL, info-micro@BRL
Via: Mit-Mc; 11 Dec 82 2:51-EST
Via: Brl; 11 Dec 82 3:09-EST
Via: Brl-Bmd; 11 Dec 82 3:14-EST
My engineers tell me much the same thing, except that for Atari
drives Elephant disks are better than Dysans because with Atari
the thicker the medium the better; or so say they for reasons
that I did not bother to try to understand.
jepinfo-cpm (12/15/82)
>From CSTROM@Mit-Mc Mon Dec 13 01:36:37 1982
To: dag@UCBARPA.BERKELEY.ARPA
Cc: Info-CPM@BRL
Via: Mit-Mc; 11 Dec 82 8:49-EST
Via: Brl; 11 Dec 82 8:55-EST
Via: Brl-Bmd; 11 Dec 82 9:03-EST
Alumina is aluminum oxide and is used as an industrial abrasive.
Floppy disks would use such a material to keep the heads clean I would
assume, although too much of it is certainly akin to inserting a
floppy sandpaper sheet rather than a diskette! It would be most
interesting to learn which vendor uses what it his medium formulation;
I am frankly weary of third-hand reports and horror stories re
diskettes - if I listened to all of them, there would certainly be no
diskette that I could use with complete confidence!
My philosophy to a certain extent is that you get what you pay for,
though I doubt one can apply this too rigidly to such a hocus-pocus
field as magnetic media. It would be nice if the manufacturers of
diskettes (and tapes too for that matter) would stop trying to snow is
and come up with some meaningful standard, industry-wide performance
specifications. It is not likely that they will.
Charlieinfo-cpm (12/15/82)
>From RMS.G.BANDY.MIT-OZ@Mit-Ml Mon Dec 13 11:11:38 1982
To: CSTROM@Mit-Mc
Cc: dag@UCBARPA.BERKELEY.ARPA, Info-CPM@BRL
In-Reply-To: Your message of 11-Dec-82 0931-EST
Via: Mit-Ml; 11 Dec 82 10:10-EST
Via: Brl; 11 Dec 82 10:21-EST
Via: Brl-Bmd; 11 Dec 82 10:39-EST
just goes to show. you usually *do* get what you pay for.
maxell makes some of the best mag. med. overall, and the best
floppies around. like i've said before, they'll take abuse
and not drop data.
-andy
-------info-cpm (12/16/82)
>From X.GYRO.MIT-OZ@BRL Mon Dec 13 18:32:13 1982
Sender: X.GYRO.MIT-OZ@BRL
To: Charlie Strom <CSTROM@Mit-Mc>
Cc: info-cpm@BRL
In-Reply-To: The message of 11 Dec 1982 08:36-EST from Charlie Strom <CSTROM at Mit-Mc>
Via: Mit-Mc; 11 Dec 82 11:50-EST
Via: Brl; 11 Dec 82 11:56-EST
Via: Brl-Bmd; 11 Dec 82 11:59-EST
A friend of mine at DEC was responsible for designing the drives and
selecting the media for the DEC PCs. He did extensive head wear
testing of various diskettes with the following interesting result:
Maxell disks had the lowest error rate, but were by far the most
abrasive. Dysan and Verbatim Datalife were almost as low in errors,
and much less abrasive. (I think he finally picked Datalife, but I'm
not sure.) But the point is, watch out for Maxell! (And especially
don't mix them with other disks -- a little of the abrasive remains on
the heads and will rapidly destroy softer coatings.)
-- Scottinfo-cpm (12/16/82)
>From POURNE@Mit-Mc Mon Dec 13 23:37:06 1982
To: X.GYRO@Mit-Mc
Cc: CSTROM@Mit-Mc, info-cpm@BRL
Via: Mit-Mc; 12 Dec 82 2:49-EST
Via: Brl; 12 Dec 82 2:57-EST
Via: Brl-Bmd; 12 Dec 82 3:39-EST
Thank you. I had not known about Maxell disks.
Query: does anyone have a program that will cause the
heads to load although nothing is being read? This to allow use
of head cleaning disks. I suppose this might be specific to the
controller used? I have a CompuPro Disk One in two separate
machines (8085/8088 and z-80). It's nt simple to get them to
clean the heads, or is it?info-cpm (12/16/82)
>From Gumby.MIT-OZ@BRL Tue Dec 14 01:45:40 1982
To: Jerry E Pournelle <POURNE@Mit-Mc>
Cc: info-cpm@BRL
Via: Mit-Mc; 12 Dec 82 17:28-EST
Via: Brl; 12 Dec 82 17:49-EST
Via: Brl-Bmd; 12 Dec 82 17:52-EST
Date: 12 December 1982 02:53-EST
From: Jerry E Pournelle <POURNE@Mit-Mc>
Query: does anyone have a program that will cause the
heads to load although nothing is being read? This to allow use
of head cleaning disks. I suppose this might be specific to the
controller used? I have a CompuPro Disk One in two separate
machines (8085/8088 and z-80). It's nt simple to get them to
clean the heads, or is it?
It's surprisingly simple. You can write a simple basic program or just
do it interactively. Look up the controller IO addressses in your manual
and then look up which numbers cause the heads to seek to track 77. You
can then just do OUT xx,yy for the appropriate values of xx and yy. be
careful about hax and decimal! your manual will probably give you the
numbers in HEX or OCTAL! Either convert them yourself or have basic do
it for you.