WD1001FALS Rom dump comparison

[nikey22]

I'm curious, I have 2 hard drives nearly identical, infact the serial number is only 8 digits behind the other one. Yet, in the ROM dumps, I still see some differences in the preamp values and microjogs. What are those? What do they mean?

P.S. swapping out the ROMs between the 2 drives, they both read fine and behave 100% normally. Thanks!

Attachments

[labtech]

https://blog.acelaboratory.com/tag/microjogs

[fzabkar]

HDD from inside: Tracks and Zones:
http://hddscan.com/doc/HDD_Tracks_and_Zones.html

The following patent document has a good explanation of microjogs:
http://patentimages.storage.googleapis.com/pdfs/US5978168.pdf

[nikey22]

@labtech
@fzabkar
thank you both, those were excellent reads. I have a new appreciation for these intricate devices!
I heard there are modules in the SA that will re-compute the mircojogs for you, to optimize throughput? Any thoughts on this? Thanks.