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:
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.
Don't 'most' hard drives use perpendicular recording these days?
Triples data density, for one...
ymmv
Very nice!
Inductive is oldschool. but not wrong.
I think It should be some sort of RLL, differential manchester is extremely oldschool.
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.
I should have. They would like it.
Oh no, I didn't know it was possible with javascript until I saw that.
Tom Del Rosso wrote
That?s a very superficial/dumbed down view of what actually happens.
Yeah, its quite elegantly done.
Probably appropriate for the intended audience. Neatly done I thought.
A few years ago someone showed me this: (or something very similar)
I was thinking in terms of a balanced signal, then realized the encoding didn't have to be balanced.
Inductive is very historic.
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.
Not really. Unless you are trying to fix a very old tape data recorder, this animation is irrelevant today.
Arno
Manchester produces a balanced signal. That's what I was thinking of. Balance isn't needed for this apparently.
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.
Oh, I see. That is actually interesting. Agreed.
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
Check this out:
Tim
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