brown@CMU-CS-K.ARPA (Andy Brown) (07/11/85)
Whether it is a good idea to use both sides of a floppy disk depends
on two things:
1) Is the magnetic material on both sides of the disk error-free.
2) Are the disks designed to be "flipped". That is, can the disk
safely rotate in both directions with no damage.
Most floppy disks are manufactured with a magnetic coating on *both*
sides. The disks are then tested to make sure that there are no
defects which would make them unsuitable for data storage. If one
side of a disk is bad, then it is usually ceritfied as a single-sided
disk, if both sides are good, then it is certified as a double-sided
disk. When you buy blank disks, it will always say on the box whether
the disks are single or double sided. Therefore, most single-sided
disks have *known* defects on the uncertified side (you can tell which
side is the correct side because it has the label on it).
All floppy disks have what is known as a "liner". This is inside the
cover of the disk and it has two main functions: to minimize friction
as the disk is spinning; and to catch and redirect any dirt and dust
which may have found its way into the disk jacket. There are a wide
variety of liner designs, and some of them are intended for use with
disks that will only be spinning in *one* direction. Flipping a disk
with such a liner could cause dirt and dust that was trapped by the
liner to be released onto the disk, creating the potential for head or
disk damage.
It must be mentioned that there are really *two* kinds of double-sided
disks. Some disk drives, (such as the double sided drives in the IBM
PC) have two heads, one for each side of the disk. Thus they use both
sides of the disk, but the disks always spin in the same direction.
When you "flip" a disk on a single-sided disk drive, such as the
Commodore 1541, the disk will spin in the opposite direction when you
flip it. Thus there are some floppy-disks on which both sides can be
used, but you might not want to use the *back* side on your Commodore
1541 disk drive because using that side will cause the disk to spin in
the wrong direction.
It is absolutely safe to use both sides of a disk on a 1541 disk-drive
if the disks are certified double-sided on the box, and there is a
write-protect notch cut on both side edges of the disk. If not, then
it is risky to use the uncertified side for data storage.
If you buy a commercial software product which uses both sides of a
disk, then it is probably safe to assume that they are using the
correct kind of disk.
--- Andy Brown oyster@uwmacc.UUCP (Vicious Oyster) (07/11/85)
In article <11475@brl-tgr.ARPA> brown@CMU-CS-K.ARPA (Andy Brown) writes: > >Most floppy disks are manufactured with a magnetic coating on *both* >sides. The disks are then tested to make sure that there are no >defects which would make them unsuitable for data storage. If one >side of a disk is bad, then it is usually ceritfied as a single-sided >disk, if both sides are good, then it is certified as a double-sided >disk. When you buy blank disks, it will always say on the box whether >the disks are single or double sided. Therefore, most single-sided >disks have *known* defects on the uncertified side (you can tell which >side is the correct side because it has the label on it). > If this is really the way it works, why is the "correct" side of the disks I buy *always* on the same side, i.e. the "wrong" side has the seams? Or can they be tested before putting them in the envelope? Tune in next week for the answer to this and other pressing world problems... -- - joel "vo" plutchak {allegra,ihnp4,seismo}!uwvax!uwmacc!oyster "Take what I say in a different way and it's easy to say that this is all confusion."
dgary@ecsvax.UUCP (D Gary Grady) (07/12/85)
> From brown@CMU-CS-K.ARPA (Andy Brown) Wed Dec 31 19:00:00 1969 > . . . Therefore, most single-sided > disks have *known* defects on the uncertified side (you can tell which > side is the correct side because it has the label on it). I have not found this to be the case in practice. I believe Andy is correct that diskettes with one bad side are sold as single-sided diskettes, but experience suggests that the main difference between the single and double-sided varieties is the label and the price. (This is probably why the price difference is so low now.) At one time manufacturers claimed that single-sided disk jackets lacked some sort of treatment or lubricant on one side. I've ripped apart several of the plastic jackets of different brands and I have never seen a difference. I have only rarely had a problem using single sided diskettes in double sided drives. However, the cost difference is now so low that I go ahead and get double-sided ones. -- D Gary Grady Duke U Comp Center, Durham, NC 27706 (919) 684-3695 USENET: {seismo,decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary
ugthomas@sunybcs.UUCP ( Timothy Thomas) (07/14/85)
> > . . . Therefore, most single-sided > > disks have *known* defects on the uncertified side (you can tell which > > side is the correct side because it has the label on it). I have well over 200 SS/SD disks that I have been using for about 3 years on both sides. I have had relatively few problems (probably about 5 disks out of all of them have failed, and only when the disk was being written for the first time, so no info was lost). The only difference between SS and DS are that the DS are *certified* to be used on both sides. True the disk is not meant to be spinned backwards, but for the savings in money (let alone storage space) I think it is worth it. -- ____________ ____/--\____ \______ ___) ( _ ____) "Damn it Jim!, __| |____/ / `--' I'm a programmer not a Doctor!" ) `|=(- \------------' Timothy D. Thomas SUNY/Buffalo Computer Science UUCP: [decvax,dual,rocksanne,watmath,rocksvax]!sunybcs!ugthomas CSnet: ugthomas@buffalo, ARPAnet: ugthomas%buffalo@CSNET-RELAY
johnl@ima.UUCP (07/15/85)
/* Written 7:57 am Jul 11, 1985 by brown@brl-tgr in ima:net.micro */ /* ---------- "using both side of disks" ---------- */ > Therefore, most single-sided disks have *known* defects on the > uncertified side (you can tell which side is the correct side because > it has the label on it). This used to be true, but for the past several years it appears that most floppy disks, whether labelled single or double sided, are in fact good on both sides. (This is a testimony to the quality of disk manufacturers -- they're making better media than they need.) I know lots of people who buy single sided disks rather than double sided, but then format and use them as double sided. The difference in price far outweighs the cost of throwing away about one out of 30 that is only good on one side. If you're really paranoid about your data being super reliable and clean, you might want to pay extra for nominally double sided disks, but if you really care about long term stability of your data, floppy disks are a poor choice in any event. John Levine, ima!johnl
werner@aecom.UUCP (Craig Werner) (07/17/85)
> >disk. When you buy blank disks, it will always say on the box whether > >the disks are single or double sided. Therefore, most single-sided > >disks have *known* defects on the uncertified side (you can tell which > >side is the correct side because it has the label on it). > > One should probably assume the above to be true, but in my experience with Maxell MD-1s (single-sided), I have all but three of the last 280 format as double-sided, and 2 of the remaining 3 had one defect in Track 39 (last track). The one remaining disk lost 10K in bad tracks. Not a bad cost/ performance experience over using MD-2s. (I'm 10 for 10 with Fujis too.) -- Craig Werner !philabs!aecom!werner "The world is just a straight man for you sometimes"
rlk@wlcrjs.UUCP (Richard L. Klappal) (07/17/85)
[] I don't know if there is any truth to "they're not made to run backward"; they seem to be preety even in that regard to me. What I don't want is the dust/dirt/whatever that collects on the inner sleeve being spread back over the disk/head and eating a groove thru the media. Take a look at the back side of a diskette that has seen heavy use in a single sided drive and tell me if you want that groove occupying legit data areas. If you need both sides, get double sided drives, -- unless you don't put any value on your work/time. Richard Klappal UUCP: ..!ihnp4!wlcrjs!uklpl!rlk | "Money is truthful. If a man MCIMail: rklappal | speaks of his honor, make him Compuserve: 74106,1021 | pay cash." USPS: 1 S 299 Danby Street | Villa Park IL 60181 | Lazarus Long TEL: (312) 620-4988 | (aka R. Heinlein) -------------------------------------------------------------------------
cdl@mplvax.UUCP (Carl Lowenstein) (07/24/85)
In article <749@wlcrjs.UUCP> rlk@wlcrjs.UUCP (Richard L. Klappal) writes: > >Take a look at the back side of a diskette that has seen >heavy use in a single sided drive and tell me if you want that groove >occupying legit data areas. > If by 'back side' you mean the side away from the label, that groove *is* the data area. The head is on the bottom. -- carl lowenstein marine physical lab u.c. san diego {ihnp4|decvax|akgua|dcdwest|ucbvax} !sdcsvax!mplvax!cdl