Overclocking the XO-1

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Warnings

By overclocking your OLPC you are running the hardware outside the design specifications. Overclocking your CPU and/or RAM may cause stability problems, data errors, and possibly hardware damage. As the OLPC is passively cooled, physical damage could easily be caused by excess heat.

The procedure detailed below is relatively safe, cpu and memory voltages are not changed, as that appears to require a hardware hack.

How to

First, get to an Open Firmware Ok prompt.

Type the following commands:

ok 4c000014
ok rdmsr
ok u.
ok u.

After this, two hex values will be displayed. Write down the second one that is displayed. For example, this may display 7de009e.

Now you must choose how much to over (or under) clock your CPU and RAM speeds.

The table below lists the value you will need to overclock, and what speeds this value over (or under) clocks the CPU and RAM to.

Value CPU speed RAM speed
3d3 333 MHz 133 MHz
3d5 366 MHz 133 MHz
3d7 400 MHz 133 MHz
3d9 433 MHz 133 MHz
3db 466 MHz 133 MHz
3dd 500 MHz 133 MHz
3df 533 MHz 133 MHz
3e1 566 MHz 133 MHz
4d3 333 MHz 166 MHz
4d5 366 MHz 166 MHz
4d7 400 MHz 166 MHz
4d9 433 MHz 166 MHz
4db 466 MHz 166 MHz
4dd 500 MHz 166 MHz
4df 533 MHz 166 MHz
4e1 566 MHz 166 MHz
5d3 333 MHz 200 MHz
5d5 366 MHz 200 MHz
5d7 400 MHz 200 MHz
5d9 433 MHz 200 MHz
5db 466 MHz 200 MHz
5dd 500 MHz 200 MHz
5df 533 MHz 200 MHz
5e1 566 MHz 200 MHz
653 333 MHz 216 MHz
655 366 MHz 216 MHz
657 400 MHz 216 MHz
659 433 MHz 216 MHz
65b 466 MHz 216 MHz
65d 500 MHz 216 MHz
65f 533 MHz 216 MHz
661 566 MHz 216 MHz
6d3 333 MHz 233 MHz
6d5 366 MHz 233 MHz
6d7 400 MHz 233 MHz
6d9 433 MHz 233 MHz
6db 466 MHz 233 MHz
6dd 500 MHz 233 MHz
6df 533 MHz 233 MHz
6e1 566 MHz 233 MHz

Now it's time to do the overclocking itself.

Type the hex value you wrote down in the previous step into the prompt and press Enter. Then type the overclocking value you chose into the prompt and press Enter.

Next, type the following:

ok 4c000014
ok wrmsr

If it worked, it will appear that nothing has happened. If you have pushed the settings too far your system may have frozen or spontaneously rebooted, just power off and choose a more conservative setting and try again.

Your XO-1 is now overclocked! Keep in mind that this overclock is only persistent until the system is rebooted. Making it permanent is an exercise left to the reader.

References

These instructions were rewritten from a guide posted on the OLPC News Forum. The original guide can be found here.