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Set Automatic Acoustic Management level on hard drives
Authored by: alexwegel on Sep 14, '06 04:11:56PM
Hello

I love to hear that it did work for you.

Hated the continuous parking too, and turned it off altogether (not in OFW). Maybe the mini relies on it more for thermal reasons or so (just a thought).

Regarding your first question about restoring to factory settings:

According to the ATA (draft-)standard, the AAM is only active when it "has been enabled", which seems to imply to me that it is disabled initially (my new, unchanged drive confirms this).
This sounds a little fuzzy, but i couldn't find anything more specific so far.

Therefore, disabling AAM should do it.

A little bit of confusion comes from the presence of a "vendor recommended value" for the AAM setting, and the spurious mention of a "default value", which might be that recommended value, especially as it does not seem to be specified (even mentioned) anywhere else in the text. And then there is the value zero for "vendor specific value".
My guess is, that they all end up being the same.

Therefore, disabling AAM should still do it.

..unless the HD doesn't implement it (even if enabling is implemented, disabling might not be, according to the standard).. A possible fallback option would be setting AAM to zero, but i doubt there's a drive implementing only one of them.

Code Time!

Disable AAM for boot-disk (by its devalias "hd"):

0 0 0 here C20000 , ef , 4000 1 apply ata-command hd . 

Fallback option: Set AAM value of boot-disk to "vendor specific" (i.e. 00)

0 0 0 here 420000 , ef , 4000 1 apply ata-command hd . 


Now to question two: Do those settings "stick" with the hard drive?

The settings stick, at least the AAM stuff and other drive settings.
The AAM hack doesn't affect OFW or OS settings, but rather uses OFW as a tool to talk to the HD itself.
This could also be done later after booting, but that would be (a) much more involved, and (b) no forth -> no fun :-)

Question 3 is easy: You have to run the command on each new drive (once).

BTW: The commands can be put into text files, and be run from the OFW prompt, e.g.:

----- save following lines to file "aamoff.of" at the root dir of your boot volume

\ <- the first line must start like this to be recognized by OFW. this is a comment
\ Run this file by typing the following at the OFW prompt (without the leading "\  "):
\     boot hd:\aamoff.of
\ then type
\     mac-boot
\ to continue booting

.( Disabling AAM on boot drive) cr                     \ print a message
0 0 0 here C20000 , ef , 4000 1 apply ata-command hd   \ do it
.( Result: ) . cr                                      \ report (0=OK)

\ end of file
-------

This might be handy, because it also has the docs built in :-)

The file for turning AAM on, and doing the same for drive 2 is left as a homework ;-)


Anyway, i enjoyed the digging, and while at it, duely silenced my new hd (do you believe in coincidence? :-)

Cheers,
Alex

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