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Author Topic: HDD from inside: Tracks and Zones  (Read 11630 times)
Doomer
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« on: October 27, 2009, 06:02:56 PM »

Here we can discuss this article - http://hddscan.com/doc/HDD_Tracks_and_Zones.html
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fzabkar
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« Reply #1 on: October 31, 2009, 01:57:57 PM »

Thank you for a very informative tutorial.

I notice that the author of Spinrite claims to be able to influence the behaviour of the AGC circuit in a drive's read preamp. He does this by training the AGC circuit with a data pattern designed to produce a maximum flux amplitude, and then following it up with a minimum amplitude flux pattern. He claims that this technique will uncover weak sectors.

Here is Steve Gibson's explanation:

http://www.grc.com/srphysics.htm

Your tutorial includes the following picture of a modern data sector:

http://en.rlab.ru/doc/images/HDD_Tracks_and_Zones/data.jpg

I'm wondering whether the read gain established during the AGC preamble persists throughout the entire data sector, in which case Gibson's claims would no longer be true, assuming they ever were. Or is the AGC active throughout the entire data field, in which case the gain could vary?

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Doomer
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« Reply #2 on: October 31, 2009, 09:21:57 PM »

As I wrote in my article data in data sectors stored scrambled and more than that - different drives do it different way (because part of scrambling system is proprietary and every manufacturer does it unique way)
So the main conclusion from this knowledge - there is NO WAY (for regular software) you can write "low amplitude pulses" or "high amplitude pulses" on the drive because drive is not going to write what you send to it. Data is going to be scrambled before it's actually going to be written to a drive's surface preventing read channel synchronization loss

You can figure everything else in "SpinRite magic" doesn't make sense after you know how drive writes
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