On Aug 27, 2010, at 3:01 PM, Matt Rhinesmith wrote:
This DOES work, and it proves that this is so in one simple way. If
reset the PRAM, it still says 533 MHz. If you try that with the
speed-changing commands, it resets itself on every PRAM wipe.
Nope, you're wrong. This is written to NVRAM, not PRAM. Resetting the
PRAM doesn't reset the NVRAM. I'll PROVE you wrong. Boot to Open
Firmware using Cmd-Opt-O-F.
At the Open Firmware prompt, type:
set-defaults<Return>
reset-all<Return>
where <Return> means hit the Return key. The replies should be "OK" to
the first command, and a restart to the second command.
NOW you'll see that your "About this Mac" and "System Profiler" are
back to their normal settings, and are showing you the REAL speed of
you Mac, which HASN'T CHANGED.
What you were doing was simply changing the value stored in the NVRAM
that tells the About this Mac & System Profiler what the speed is. If
you change the speed of a Mac FOR REAL by moving the required jumpers
(or soldered on resistor jumpers) AND the new speed ISN'T one of the
speeds available in the look-up table in the firmware, THEN the About
this Mac & System Profiler will say "0 MHz" or default to a lowest
possible MHz, both of which will be WRONG, the HARDWARE jumpers set
the ACTUAL speed, and the # shown in About this Mac and System
Profiler ISN'T from an actual test, it simply comes off a value stored
in a look-up table in the firmware which is copied over to NVRAM. What
you've done is copied a FAKE number into NVRAM and now it shows your
FAKE speed. If you want, I can supply you with a list of more FAKE
speeds, and you can play around and make your clamshell iBook say that
it's 1.67 GHz if you want, but that won't make it 1.67 GHz. You'll be
lucky to overclock 15-20%, and 10% would likely be best. Anything
greater and you'll likely overheat your CPU and burn up your Mac
without some significant cooling modifications.
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