[Ti] sysctl hw.cpufrequency - PROBLEM

[Kynan Shook]

etyrnal at ameritech.net writes:
> I've heard some people CLAIM that this command does not report the
> correct speed...
> This makes no sense...  I would estimate that if the command did, in
> fact, report incorrectly that it would doone of the following odd
> behaviours:
> 1.) ALWAYS report one wrong speed - regardless of any changes.
> 2.) Report a VERY wrong speed - eg: 0MHz or 439.7256497537 MHz or some
> other 'broken' sounding number.

These are certainly possible ways for something to break, but, what if  
bus slewing is on?  The CPU and bus speeds are changing continuously,  
and I can tell you for sure that sysctl does NOT properly update.  In  
fact, sysctl doesn't immediately show the proper speed on either my 12"  
or my 17" PowerBooks when I switch to reduced CPU speed; if I  
restarted, I'd likely see the correct speed, I imagine, but I don't  
feel like rebooting.  The best way to check the speed you're running at  
is to run Skidmarks GT (part of the Apple Developer Tools) and see how  
your computer compares to the base (PowerMac G4 1.0 GHz = 100), but  
even moreso, to compare results against yourself, as comparing with  
other computers is likely to produce inconsistent results sometimes.

Anyway, running Skidmarks GT, I get about 67 on each test when at  
reduced processor speed, and about 100 when at full (my 1 GHz 17" drops  
to 667).  I'd recommend checking out this app, since sysctl does NOT  
always report the correct speed.  Surveying various online forums, most  
people who tested with Skidmarks or some other reputable benchmark tool  
found that sysctl was incorrect on their machines, though there are  
certainly some cases where sysctl is reporting correctly.

> NOW - all of this is ESPECIALLY strange to me as it was my
> understanding that the 867MHz models do NOT do Processor Speed Changes
> at all...  it was my understanding that the main method of on-battery
> power-savings was achieved via disabling the L2 and or L3 cache
> memory...  and possibly by the user disabling unnecessary ports eg:
> modem, airport, enet, irda, etc...

Actually, yours does change speed; both the 1 GHz and 867 MHz Ti models  
drop to 667 MHz.  Other PowerBooks have similar changes.  Additionally,  
the L3 cache is disabled.  Obviously, you should check Energy Saver (be  
sure to check BOTH power adapter and battery settings) and make sure  
it's at the desired setting.  If it is (and you've checked out  
Skidmarks), I have a whole bunch of things for you to try, coming up  
soon.  However, other causes of running at reduced speed are running  
with no battery installed, running with a low battery charge, running  
off of airline power or any other similar power-limited power adapter  
(eg, not the power adapter your computer shipped with), possibly during  
system startup, if the computer is too hot, and some other causes,  
depending on your model.

Anyway, here are the things I would recommend trying.  It will take  
longer, but I'd recommend trying them one at a time to see if you can  
identify which one fixes the problem.  Be sure to check with Skidmarks  
each  time you try as well, since sysctl does NOT always report the  
correct value.  It might be worth adjusting the CPU speed in Energy  
Saver, switch to Skidmarks, check your performance, change the CPU  
speed again, and test in Skidmarks again, see what sort of a difference  
you get.  In most cases, your difference should be at least 10 or 20  
points, if your CPU is running at a different speed.  If your computer  
supports it, don't use Automatic for the testing; this will  
automatically adjust between high and low speeds depending on the  
processor usage, and you will not get correct results.

First, check the Options pane in Energy Saver.  Be sure to check both  
the power adapter and the battery settings.  You'll need to click Show  
Details if you haven't already to be able to adjust the CPU speed.  I'd  
recommend rebooting to check, even though the processor speed change  
will be immediate (you might want to test in Skidmarks both before and  
after rebooting).

Next, delete the file  
/Library/Preferences/SystemConfiguration/ 
com.apple.powermanagement.plist, reboot, adjust your Energy Saver  
settings, reboot again.

Reset PRAM; reboot, and hold Command-Option-p-r until you hear at least  
3 boot chimes.

Reset the Power Management Unit: see  
http://docs.info.apple.com/article.html?artnum=14449 for instructions;  
for most PowerBooks and iBooks, you shut down and either press the  
reset button, or press Shift-control-option-power.  Your date should be  
reset when you do this.  If not, you didn't do it correctly.

Reset Open Firmware.  Reboot, holding Command-Option-o-f.  You will be  
brought to a white command-line screen.  Type reset-nvram, press  
return, type reset-all, press return.  Your computer will turn off from  
this.

If you still are running at reduced speed, I'd recommend trying to boot  
from a different boot disk, preferably an archive and install, or  
better yet, erase and install.  Check your speed there.  If you really  
feel like getting dirty, try it with a few different versions of the  
OS, make sure that it's not a bug that snuck in somewhere.

If you still have problems after all that, it's possible that you have  
a hardware problem.  I'd suspect either the PMU/battery board or the  
logic board, depending on the model.  But it's by no means certain.   
Yours is a fairly unusual problem.

Anyway, just in case I haven't hammered it in enough yet, do NOT trust  
sysctl.  It is often incorrect (though not always).
HTH,