Data write/read and peak detector animation

Discussion in 'Storage Devices' started by Tom Del Rosso, Aug 4, 2012.

  1. http://www.grc.com/animation.htm

    Comments?

    I know, the read head should be magneto-resistive instead of inductive.

    But should it be Differential Manchester? The square wave transitions are
    not encoded like this:

    http://en.wikipedia.org/wiki/Differential_Manchester_encoding


    For some people the most interesting thing is that the animation is coded in
    javascript, with no flash or similar, and it's neatly hand-coded and
    commented, so you might want to save the source for future reference.


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    Tom Del Rosso, Aug 4, 2012
    #1
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  2. Tom Del Rosso

    Jasen Betts Guest

    On 2012-08-04, Tom Del Rosso <> wrote:
    >
    > http://www.grc.com/animation.htm
    >
    > Comments?


    Very nice!

    > I know, the read head should be magneto-resistive instead of inductive.


    Inductive is oldschool. but not wrong.

    > But should it be Differential Manchester? The square wave transitions are
    > not encoded like this:


    I think It should be some sort of RLL, differential manchester is
    extremely oldschool.

    > http://en.wikipedia.org/wiki/Differential_Manchester_encoding
    >
    >
    > For some people the most interesting thing is that the animation is coded in
    > javascript, with no flash or similar, and it's neatly hand-coded and
    > commented, so you might want to save the source for future reference.


    No crosspost to comp.lang.javascript :)

    Your code?

    The author has left the mouse coordinates display turned on
    in the lower right corner. (when I put debug code in javascript I
    use a hidden activation method eg: enable it with a key value in
    location.hash or location.hostname)

    The doctype is wrong, the document is not HTML4.01 Transitional.

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    Jasen Betts, Aug 4, 2012
    #2
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  3. Jasen Betts wrote:
    >
    > No crosspost to comp.lang.javascript :)


    I should have. They would like it.


    > Your code?


    Oh no, I didn't know it was possible with javascript until I saw that.


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    Tom Del Rosso, Aug 4, 2012
    #3
  4. Tom Del Rosso

    Rod Speed Guest

    Tom Del Rosso <> wrote

    > http://www.grc.com/animation.htm


    > Comments?


    That’s a very superficial/dumbed down view of what actually happens.

    > I know, the read head should be magneto-resistive instead of inductive.


    > But should it be Differential Manchester? The square wave transitions are
    > not encoded like this:


    > http://en.wikipedia.org/wiki/Differential_Manchester_encoding


    > For some people the most interesting thing is that the animation is coded
    > in javascript, with no flash or similar, and it's neatly hand-coded and
    > commented, so you might want to save the source for future reference.


    Yeah, its quite elegantly done.
     
    Rod Speed, Aug 4, 2012
    #4
  5. Tom Del Rosso

    Jasen Betts Guest

    On 2012-08-04, Tom Del Rosso <> wrote:
    >
    > Jasen Betts wrote:
    >>
    >> No crosspost to comp.lang.javascript :)

    >
    > I should have. They would like it.
    >
    >
    >> Your code?

    >
    > Oh no, I didn't know it was possible with javascript until I saw that.


    A few years ago someone showed me this: (or something very similar)

    http://www.elizium.nu/scripts/lemmings/

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    Jasen Betts, Aug 4, 2012
    #5
  6. Jasen Betts wrote:
    > On 2012-08-04, Tom Del Rosso <> wrote:
    > >
    > > http://www.grc.com/animation.htm
    > >
    > > Comments?

    >
    > Very nice!
    >
    > > I know, the read head should be magneto-resistive instead of
    > > inductive.

    >
    > Inductive is oldschool. but not wrong.
    >
    > > But should it be Differential Manchester? The square wave
    > > transitions are not encoded like this:

    >
    > I think It should be some sort of RLL, differential manchester is
    > extremely oldschool.


    I was thinking in terms of a balanced signal, then realized the encoding
    didn't have to be balanced.


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    Tom Del Rosso, Aug 5, 2012
    #6
  7. Tom Del Rosso

    Arno Guest

    In comp.sys.ibm.pc.hardware.storage Tom Del Rosso <> wrote:

    > http://www.grc.com/animation.htm


    > Comments?


    > I know, the read head should be magneto-resistive instead of inductive.


    Inductive is very historic.

    > But should it be Differential Manchester? The square wave transitions are
    > not encoded like this:


    > http://en.wikipedia.org/wiki/Differential_Manchester_encoding


    Manchester is also historic. All modern drives use some PRML
    decoding, i.e. the signal is read analog and the decoding
    and error correction coding takes that into account. The
    encoding itself is also a lot more sophisticated than in
    the old RLL or MFM days.

    > For some people the most interesting thing is that the animation is coded in
    > javascript, with no flash or similar, and it's neatly hand-coded and
    > commented, so you might want to save the source for future reference.


    Not really. Unless you are trying to fix a very old tape data
    recorder, this animation is irrelevant today.

    Arno

    --
    Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
    GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
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    Arno, Aug 6, 2012
    #7
  8. Arno wrote:
    >
    > Manchester is also historic. All modern drives use some PRML
    > decoding, i.e. the signal is read analog and the decoding
    > and error correction coding takes that into account. The
    > encoding itself is also a lot more sophisticated than in
    > the old RLL or MFM days.


    Manchester produces a balanced signal. That's what I was thinking of.
    Balance isn't needed for this apparently.


    > > For some people the most interesting thing is that the animation is
    > > coded in javascript, with no flash or similar, and it's neatly
    > > hand-coded and commented, so you might want to save the source for
    > > future reference.

    >
    > Not really. Unless you are trying to fix a very old tape data
    > recorder, this animation is irrelevant today.


    I meant for those who write javascript. It's ability to do this was a
    revelation to me.

    The author's purpose was to explain something about Spinrite, the old disk
    tool. He claims it does more thorough testing than a long self test. I
    doubt it, but he is a good programmer. I told him recently he should put
    that talent to use on a new product, but people still buy Spinrite. It has
    a following, like fans.


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    Tom Del Rosso, Aug 6, 2012
    #8
  9. Tom Del Rosso

    Arno Guest

    In comp.sys.ibm.pc.hardware.storage Tom Del Rosso <> wrote:

    > Arno wrote:
    >>
    >> Manchester is also historic. All modern drives use some PRML
    >> decoding, i.e. the signal is read analog and the decoding
    >> and error correction coding takes that into account. The
    >> encoding itself is also a lot more sophisticated than in
    >> the old RLL or MFM days.


    > Manchester produces a balanced signal. That's what I was thinking of.
    > Balance isn't needed for this apparently.



    >> > For some people the most interesting thing is that the animation is
    >> > coded in javascript, with no flash or similar, and it's neatly
    >> > hand-coded and commented, so you might want to save the source for
    >> > future reference.

    >>
    >> Not really. Unless you are trying to fix a very old tape data
    >> recorder, this animation is irrelevant today.


    > I meant for those who write javascript. It's ability to do this was a
    > revelation to me.


    Oh, I see. That is actually interesting. Agreed.

    > The author's purpose was to explain something about Spinrite, the old disk
    > tool. He claims it does more thorough testing than a long self test. I
    > doubt it, but he is a good programmer. I told him recently he should put
    > that talent to use on a new product, but people still buy Spinrite. It has
    > a following, like fans.


    And it is completely bogus today, basically a scam. Hence
    my negative reaction to it. As modern disks and controllers
    do not offer the interface MFM and RLL drives offered (you
    could do a raw digital reading of the data). The equivalent is
    not even possible today without uploading specialized firmware
    to the drive or using secret vendor functionality. There
    certainly is no standardized interface for asking the drive
    to give you the analog signal. And the on-disk encoding is
    also not standardized. SpinRite would need both to do any
    better than a long selftest.

    With MFM/RLL that was all different, and SpinRite did indeed
    do better. These days are over, but the SpinRite fans
    do not understand that. They just want their "god" tool
    and feel superiour.

    Arno
    --
    Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email:
    GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F
    ----
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    Arno, Aug 6, 2012
    #9
  10. Tom Del Rosso

    Tim Williams Guest

    Tim Williams, Aug 7, 2012
    #10
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