ir320@sdcc6.UUCP (ir320) (03/11/85)
I had seen ads advertising a device to erase floppy disks much as a
tape eraser works on cassettes. I had heard that this increases the
life of old disks, much as tape life is extended (or at least the
usefulness of old tape) by the tape eraser. The device claimed to
allow disks to have their lives extended via a "repositioning of the
magnetic particles on the disk to the pattern they were set at by the
factory." This doesn't sound quite kosher. Can disk life REALLY be
extended by periodic erasing?
John Antypas
UC San Diego
uucp: ...!{ucbvax,ihnp4,noscvax}!sdcsvax!sdcc6!ix255
arpa: sdcsvax!sdcc6!ix255@{Nosc,Berkeley}
sdcc6!ix255@sdcsvax.arpacfiaime@ihnp4.UUCP (Jeff Williams) (03/13/85)
> I had seen ads advertising a device to erase floppy disks much as a > tape eraser works on cassettes. I had heard that this increases the > life of old disks, much as tape life is extended (or at least the > usefulness of old tape) by the tape eraser. The device claimed to > allow disks to have their lives extended via a "repositioning of the > magnetic particles on the disk to the pattern they were set at by the > factory." This doesn't sound quite kosher. Can disk life REALLY be > extended by periodic erasing? 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? jeff williams AT&T Bell Laboratories Naperville, Ill. ihnp4!cfiaime
shor@sphinx.UChicago.UUCP (Melinda Shore) (03/13/85)
[] > From: cfiaime@ihnp4.UUCP (Jeff Williams) > 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? I have no idea whether or not using a bulk eraser will extend the life of a disk, but it certainly will clobber the disk formatting. This is no big deal -- I have yet to see *any* microcomputer that doesn't come with disk formatting software. -- Melinda Shore University of Chicago Computation Center uucp: ...!ihnp4!gargoyle!sphinx!shor Mailnet: staff.melinda@uchicago.mailnet Bitnet: shor%sphinx@uchicago.bitnet ARPA: staff.melinda%uchicago.mailnet@mit-multics.arpa
bmw@aesat.UUCP (Bruce Walker) (03/14/85)
[Quotes edited:] >> I had seen ads advertising a device to erase floppy disks much as a >> tape eraser works on cassettes. [ ...... ] Can disk life REALLY be >> extended by periodic erasing? > >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. > >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? > > jeff williams > ihnp4!cfiaime These (last) comments definitely do NOT apply to the PC, or almost any other 8 inch or 5.25 inch floppy disk system I've heard of. The new Drivetec 5.25" high capacity drives (3 Mbytes or something) use embedded servo info and those floppies need factory formatting, but most other drives use open-loop step motor positioners which couldn't care less about what's recorded on the media. I am not going to conjecture about whether diskette life can be extended but I don't feel that the average user will derive any benefits from bulk erasing his disks. *If* your heads became magnetized for some reason, you would want to demagnetize the heads and possibly bulk erase disks to prevent that from reoccurring, but that is rare. While designing disk controllers and analog read/write channels, I found that bulk erasing was useful to improve the signal-to-noise ratio for critical measurements but that was for a very specific task that shouldn't really affect normal disk operations. The trouble I can forsee with casual bulk erasing is that you have to be very careful about using the eraser or you will leave a strong magnetic "residue" on the diskette which could magnetize the heads. Should this occur, you will gradually erase the magnetic domains on each diskette you use in the affected drive. If you still want to try it, you can use a "standard" cassette/reel tape eraser such as Radio Schlock sells for under $20 and read the instructions and follow them very closely. They advise you to make sure that the eraser is several feet away from the object you wish to erase when you turn it on and keep the eraser moving in slow circles while it is on. The object of all this arm- waving is to avoid any left-over magnetic field which could be caused by the eraser's coil being ener/de-ener/gised while the 60Hz AC voltage is greater than zero and the coil is near your object. Another caveat: make sure that your DOS has a "true" disk format command before you erase any diskettes. The old DEC Rainbow didn't, but one could obtain a public-domain version from some RCP/M systems. Bruce Walker {allegra,ihnp4,linus,decvax}!utzoo!aesat!bmw
carpenter@nbs-vms.ARPA (03/15/85)
I don't know what, operating system Jeff Williams is using on his 11/23 with RX-02, which can't format disks. Some years ago when our DEC c.e. installed RT-11 on a similar setup here he left us object to a program which formats raw, blank discs on the RX-02. GiCo. This was not an "official" program, I gather. Bob Carpenter <carpenter@nbs-vms>
rhesmith@wlcrjs.UUCP (Richard H. E. Smith II) (03/16/85)
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 ========== Unfortunately, this machine isn't exactly stable. If wlcrjs goes off the net, try this mailing address: 2007 Howard, Evanston, IL 60202-3656 Thanks.
jbn@wdl1.UUCP (03/19/85)
One situation in which bulk erasing helps is when reusing disks written
on a drive with a different track width. PC/XT <=> PC/AT reuse sometimes
benefits from bulk erasing. In particular, if you want to write a disk on
an AT and read it later on an XT, it should be bulk erased and formatted at
low density on the AT before reading it on an XT. The AT writes narrower
tracks (being a higher density drive) and won't erase the entire wide track
as it overwrites, leaving some residue that gives the XT trouble unless you
bulk erase or use new disks.
However, the business about ``extending your disk life by periodically
reorienting the magnetic particles'' sounds like total bunk.
John Naglerap@oliven.UUCP (Robert A. Pease) (03/20/85)
. >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? > > jeff williams > AT&T Bell Laboratories > Naperville, Ill. > ihnp4!cfiaime This is totally true. The RX02 uses track address marks that are formated single density and the sector ids and data blocks are formated double density. The format program under RT-11 passed over the track addresses and only formated the sector ids and data fields. If we ever needed to format a totally munched disk we formated it on our MDS workstation and then reformated on the PDP. What a pain that was at times. -- Robert A. Pease {hplabs|zehntel|fortune|ios|tolerant|allegra|tymix}!oliveb!oliven!rap