OpenBSD Journal

Firmware Level Speedup (OpenBSD-macppc)

Contributed by jose on from the magic-boot-sequence dept.

Mark Grimes has recently posted a note to the OpenBSD-MacPPC list describing a way to speed up your MacPPC machine using a firmware hack:

I've seen a number of posts on how to get the unfortunate default power-saver
state from 667mhz to 800mhz, in fact I was one of those posts on the OpenBSD
list today.  I spent half a day hacking openfirmware and was met with success.
The following will do the trick.

Boot into Openfirmware

Type EXACTLY THE FOLLOWING (with spaces)


" /cpus/PowerPC,G4@0" select-dev

2faf0800 " clock-frequency" get-my-property 2drop !

00000000 " force-reduced-speed" get-my-property 2drop !

(Type Ctrl-C to exit editor)


setenv use-nvramrc? true


(Laptop will reboot, then enter normal boot hd command to boot {Open,Net}BSD)

dmesg will now report 800mhz! :)

Now note that this is really experimental, and any OpenFirmware hacking you do can render your machine unusable (I did it to one of my machines years ago!). However, if you're feeling brave and desparate for speed, this may be something to look at.

(Comments are closed)

  1. By Ben Goren () on

    I posted a similar message to misc@ earlier today, namely: just what is performance like with OpenBSD on the newer Apple hardware? How does it stack up against the other platforms?

    Does this speed hack have a noticible difference? Was the system really slow before?

    This is pure idle curiousity--I certainly can't afford any of the latest and greatest from Apple right now. Not that I don't want a dual G4 and one of those stupid-huge flatscreen displays....



    1. By jolan () on


      Well, it's the difference between running at 667mhz and running at 800mhz.

      This is for *laptops* as it clearly states in the article.

      Basically, it's the same thing as Intel's speedstep technology where the machine runs at a lower speed to save power.

  2. By deem0N () on

    I mean iBook hardware ?

  3. By Gilbert Fernandes () on

    I got an iBook running at 600 Mhz, what is the value I should use ?

  4. By Peter Hessler () on

    This is _ONLY_ for TiBooks at 800MHz, that show up as 667MHz, due to Apple's desire to save battery life. Do not use this on any other system, except for the brand spanking new TiBooks at 800MHz. No iBooks, no older TiBooks (I'm sol personally), no other systems. Doing this on a system that isn't 800MHz will break it, and void your warentee.

  5. By AC () on

    It's a bit of a pleasant surprise to see FORTH on the front page of

    1. By Jimmy () on

      i have snake in my openfirmware...
      ypu just have to love the idea of
      openfirmware with pram =)

      may the forth be with us indeed.

      / Jimmy

  6. By Mark Grimes () on

    As I have stated on openbsd-ppc list, prior to
    the posting of this article, this hack did not
    meet success. It was experimental and was an
    initial stab at the problem. Wall clock times
    and benchmark analysis will prove this point.

    The real solution is horribly more complex:

    (OpenBSD macppc users SHOULD read both lists, but
    alas I did make an effort to crosspost the fact that
    the initial hack did not work)


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