jim@cavebear.berkeley.edu (Jim Bradley) (04/29/91)
I am completely baffled by the following experience. Someone sent me eight (green) 360K 5.25-inch floppy diskettes containing pkzip archive files. I write-protected each with a silver sticker from another box of diskettes. I subsequently discovered that I could *freely* write or erase files from any of these "write-protected" diskettes in the 1.2M half-height floppy drive of an AT-clone or in the retro-fit 360K half-height floppy drive of an IBM XT. Both machines are located in a computer lab I manage. (I have not tested other machines, since I am so spooked by this experience.) When I performed the same test with the same silver stickers with the same floppy drives, but this time using diskettes from my own collection, the write-protection worked correctly. Two issues: 1) My experience (whatever the cause) suggests that write-protecting cannot be assumed to provide protection against virus infection if you stick Brand-Y diskette into Brand-X machine. 2) What is going on here? How is it possible for a diskette drive to write on one brand of protected diskette, and not on another brand. The mind boggles. Jim Bradley, CNR Computer Facility, UC Berkeley jim@cavebear.berkeley.edu
PHYS169@csc.canterbury.ac.nz (Mark Aitchison, U of Canty; Physics) (04/30/91)
jim@cavebear.berkeley.edu (Jim Bradley) writes: > I write-protected each with a silver sticker from another box of diskettes. > I subsequently discovered that I could *freely* write or erase files from > any of these "write-protected" diskettes in the 1.2M half-height floppy drive > of an AT-clone or in the retro-fit 360K half-height floppy drive of an IBM XT . > > Both machines are located in a computer lab I manage. I used to trust write-protect tabs until very recently. My main advice is: DON'T! Possibly, the reason why it sometimes fails, other than obvious loose wires, is because of light bouncing around the diskette drive. Remember, a tab over the notch should stop the light getting to the photo-detector on the other side; if it can bounce of a silvery tab, onto metalwork, and onto the detector, it is like having no tab on at all. I haven't tested my theory, but I suspect black tabs are better, and there should be little distance between the diskette and the photo-transistor or whatever. Someone may be able to answer the question as to whether the circuitry uses synchronised pulsed light, or plain light (the latter would mean daylight from outside the computer could nullify the protection system). Mark Aitchison.
jesse%altos86.Altos.COM@vicom.com (Acer - Jesse Chisholm) (05/03/91)
PHYS169@csc.canterbury.ac.nz (Mark Aitchison, U of Canty; Physics) writes: | Possibly, the reason why it sometimes fails, other than obvious loose | wires, is because of light bouncing around the diskette drive. | ... | Someone may be able to answer the | question as to whether the circuitry uses synchronised pulsed light, | or plain light (the latter would mean daylight from outside the | computer could nullify the protection system). I don't know about the pulsed or steady light, but I do know that if I leave the cover off my machine, the flourescent lights totally confuse the drive as to whether there is or isn't a write protect tab on the floppy. I have had no trouble with silvered tabs, but then, the brand I buy usually comes with black ones.
csg068@cck.cov.ac.uk (** DECKER **) (05/07/91)
jesse%altos86.Altos.COM@vicom.com (Acer - Jesse Chisholm) writes: >PHYS169@csc.canterbury.ac.nz (Mark Aitchison, U of Canty; Physics) writes: >| Possibly, the reason why it sometimes fails, other than obvious loose >| wires, is because of light bouncing around the diskette drive. I used to use red masking tape whenver I ran out of labels, but this caused problems due to the fact that some drives use infra-red light to detect a label. - -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= : DECKER : csg068@uk.ac.cov.cck : Dept. of Computer Science, Coventry Poly : : G O D F O D D E R : =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=