4F Uniqueness.
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Author:  sin [ December 16th, 2018, 16:00 ]
Post subject:  Re: 4F Uniqueness.

X-reference, https://forum.hddguru.com/viewtopic.php ... le=desktop

Foster The People - Pumped up Kicks

Author:  fzabkar [ December 16th, 2018, 16:52 ]
Post subject:  Re: 4F Uniqueness.

I would start by adjusting these parameters, one at a time.

Offset(h) 00   02   04   06   08   0A   0C   0E

000001C0  90AA 0000 A211 57F6 CA5B 3CF6 CA5B 3CF6
                    ^^^^^^^^^ head #0

000001D0  6DB0 3AF6 C590 FAFA 1751 2EFB 2E34 2DFB
                    ^^^^^^^^^ head #0
000001E0  5CFA 2AFB

They appear to be 32-bit little-endian data. I would begin by limiting my edits to the MS byte or nibble.

For example, I would make changes such as the following:

0xF65711A2 --> 0xE6nnnnnn or 0x06nnnnnn

Author:  sin [ December 17th, 2018, 8:34 ]
Post subject:  Re: 4F Uniqueness.

Thanks for guiding here. Just did another Fblite only to find 4F is unique and the threshold point location looks correct.


Author:  fzabkar [ December 24th, 2018, 16:31 ]
Post subject:  Re: 4F Uniqueness.

fzabkar wrote:
sin wrote:
The highlighted area in the edited 4F photograph displays the threshold point. Any change made beyond this point has less effect on the SA. Any changes made before this point or at this point can disallow SA access.

This observations seems contrary to expectations. AIUI, this last section of the module contains the adaptives for the dual stage actuator. :?


Sorry, I was misled.

Doomer wrote:
ShrekLT does not have dual actuators, but I must admit I mistakenly thought that important adaptives in 4F are dual-actuators related(they aren't) and even probably convinced some people of it.
Nevertheless the adaptives are important and w/o them drive won't read anything. They can be restored but it's a grueling process. There is no way to do it with PC3K.


Author:  fzabkar [ December 24th, 2018, 18:14 ]
Post subject:  Re: 4F Uniqueness.

I previously speculated that the extra data in module 4F may be related to repeatable runout (RRO). However, ISTM that the RRO values on each side of a platter should be the same, unless the servo tracks are laid down one side at a time.

By way of comparison, Samsung's drives appear to perform RRO calibration on a per platter basis rather than for each head.

PwrOn RRO1x @ H0
Table) cos = -446464, sin = 655360
Coeff) cos = -69509, sin = -3977

DiskSlip : 97 [SrvTrk]
DiskSlip : 94 [SrvTrk]

PwrOn RRO1x @ H2
Table) cos = -447488, sin = 652288
Coeff) cos = 85611, sin = -108729

DiskSlip : 97 [SrvTrk]
DiskSlip : 121 [SrvTrk]

PwrOn RRO1x @ H4
Table) cos = -450560, sin = 652288
Coeff) cos = -119334, sin = 23064

DiskSlip : 97 [SrvTrk]
DiskSlip : 104 [SrvTrk]

But maybe this is just another red herring ...

Author:  sin [ January 7th, 2019, 12:43 ]
Post subject:  Re: 4F Uniqueness.

Sorry for the delay in Reply
been very engaged with a few things.
I am really breaking my head over a CYPRESS FM4 for the final year college project.
I have to instantiate 3 adcs at once and I am not sure how to go about it.

The analog front end of the project is beautifully designed. Sorry for getting offtopic.. But that's that.


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