Open Firmware overclocking

[Chris Nelson]

I tried this last week on a lark, fairly certain that it would not work.

Unfortunately, I was right.

The cube rebooted perfectly and did report a clock speed of 533 with a 
bus speed of 133. However, testing revealed absolutely no change in 
performance from the stock 450 MHz configuration.

My totally uninformed guess is that this script alters nothing other 
than the data that is returned to Apple System Profiler by the NVRAM. 
(i.e. The cube is still running at 450 with 100 bus, but ASP is 
retrieving data for 533 with 133...)

>
> ------------------------------
>
> Message-ID: <00be01c30e6b$f4d20540$fc6250d5 at sestow2572>
> From: "Joakim Skog" <joakim.skog at home.se>
> Subject: [CUBE] Overclock a Cube through open firmware?
> Date: Tue, 29 Apr 2003 18:25:32 +0200
>
> According to the swedish Mac news site http://www.macnytt.com it 
> should be
> possible to change the bus frequency and the clock frequency on Macs 
> with a
> 100 Mhz system bus by just enter some code into open firmeware. The 
> hack
> changes the system bus to 133 Mhz and the processor speed to something 
> like
> 533 Mhz. They also note that you should check that your memory type is
> compatible with the higher bus speed before trying the hack, otherwise 
> it
> sure will crash.
>
> What do you think about this? Below is the instructions quickly 
> translated.
> Use at your own risk!
>
> /Joakim
>
> 1. Restart the computer
>
> 2. Press option+alt+o+f when restarting to enter Open Firmware.
>
> 3. write nvedit and confirm with <return> to enter the configuration 
> editor.
>
> 4. write exactly the follwoing, with spaces but without carrier 
> returns:
>
> " /" select-dev<return>
> 7efdc44 " clock-frequency" get-my-property 2drop ! <return>
> " /cpus/PowerPC,G4 at 0" select-dev<return>
> 1fca0554 " clock-frequency" get-my-property 2drop ! <return>
> 7efdc44 " bus-frequency" get-my-property 2drop ! <return>
> 1fbf711 " timebase-frequency" get-my-property 2drop !
>
> 5. press ctrl+c to exit the configuration editor.
>
> 6. write nvstore and confirm with <return>
>
> 7. write setenv use-nvramrc? true and confirm with <return>
>
> 8. write reset-all and confirm with <return> to restart the computer.
>
> If your computer is unstable after this hack, reset the pram
> (option-alt-p-r).
>