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write-protection-jumper on hard-disk

Discussion in 'PC Hardware' started by Ulrich Diez, May 21, 2005.

  1. Ulrich Diez

    Ulrich Diez Guest

    Hello!

    I have some old hard-drive in my PC. It has a jumper for write-protection.
    If that jumper is closed, the harddisk is write-protected.

    What happens if one closes that jumper while the computer/harddisk is
    still running? Could this cause severe damage to hardware?
    Where can I find more information on such questions?

    I ask for the following reason:
    At school we will do a lot assembler-programming in the next few
    months. Hereby we will also have to create some routines for reading
    from the harddrive as block-device. My experience is that it is very easy
    in assembler to screw things up. In the past I spent a lot of time on
    backing-up boot-sectors or whole partitions and reinstalling the system...
    Having the harddisk write-protected while playing around might be a
    good idea. But I don't want to open the case of the computer each time
    when write-protection is needed. So I reflect upon connecting a switch to
    the jumper-pins. But what would happen if somebody accidentally hit that
    switch while the machine is running...

    Looking forward for your replies. Thanks in advance.

    Sincerely

    Ulrich
     
    Ulrich Diez, May 21, 2005
    #1
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  2. Ulrich Diez

    modiftek Guest

    While these thing are running it is not a good idea to switch around
    jumpers and electrical connections. You most likely will damage either
    the hard drive or feedback some spiked current and overload other
    devices in the system.

    Basically those jumpers work by closing and opening small ciruitry by
    making and breaking contact with the pins. This jumping of the contacts
    will cause the devices to fail if it is done with the power on.

    Some might do it and find out that it works but, trust me, when it
    fails only then the regret steps in. Over my years I tried all kinds of
    experiments to prove the theorists in the books wrong and many times I
    learned that what they tell you in theory applies in practical also,
    although not immediately.

    Good Luck.
     
    modiftek, May 21, 2005
    #2
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  3. Ulrich Diez

    Arno Wagner Guest

    Difficult question.

    Ususlly these jumpers are queried once ad disk poer-up and
    then ignored until the next power-up.
    Possibly nothing. These jumpers are usually digital inputs with a
    10kOhm or so to V+ and the other side of the jumper grounded. So
    unless you shorten the pin to something else than its opposite pin,
    nothing in the electronics should be damaged. Whether the disk
    firmware will be confused or even notice is another question. If it
    is a really old drive you might create defective sectors when
    switching on writes. Personaly I would assume it is relatively safe to
    do what you intend. But be sure to have current backups.

    One thing you can do if you are concerned, is to use a lock-switch
    like these:

    http://tinyurl.com/dk4dm

    You should get these from any well-stocked electonics parts supplier.
    Expect to pay something between 5 and 40 Euro, depending on quality
    and design.

    Arno
     
    Arno Wagner, May 22, 2005
    #3
  4. Ulrich Diez

    Ulrich Diez Guest

    [snip]
    [snip]

    Why didn't I think about lock-switches myself?
    Of course a lock-switch is the solution!
    Thanks for the suggestion!

    Sincerely

    Ulrich
     
    Ulrich Diez, May 22, 2005
    #4
  5. Ulrich Diez

    Arno Wagner Guest

    You are welcome.

    Arno
     
    Arno Wagner, May 22, 2005
    #5
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