disabling second processor in BIOS

Discussion in 'Macintosh Computers' started by dalewalt, Apr 20, 2005.

  1. dalewalt macrumors newbie

    Apr 20, 2005
    Hi folks.

    I'm in a bit of a quandary and hope that one of you can help. To start, I've googled this, looked on apple.com, and also searched the forums, but can't find an answer to my question.

    I have a dual G4, with 10.3.8, Tiger pre-release, and 10.2 on it. To try to track down a problem with our app (Java-based), I need to disable the 2nd processor when running under Tiger. I've got the dev tools and CHUD installed on 10.3, but that doesn't help for 10.4 (and I haven't found the CHUD tools yet for Tiger).

    I *know* that there's a way to do this through the BIOS, but can't remember the syntax... can anybody help?


  2. varmit macrumors 68000


    Aug 5, 2003
    I believe that when writing the code for your program, you can designate it to see only one processor and not be a multiprocessor program. Not sure about this but it might be easier to find then the bios information. Also, you could call up Apple and ask for a senior engineer that might know what you are looking for to help solve the problem.

    You might also be better off asking something along the lines about this in the Programming area. http://forums.macrumors.com/forumdisplay.php?f=73
  3. dalewalt thread starter macrumors newbie

    Apr 20, 2005
    thanks, but won't work

    Thanks for the quick reply, varmint, but turning the processor off programmatically won't work... i'm trying to do some testing of our stuff against Tiger, and changing the program to turn a processor off will lessen the applicability of the test
  4. robbieduncan Moderator emeritus


    Jul 24, 2002
    You can do it in OpenFirmware (Macs do not have a BIOS in the traditional sense). Or you can do it in the terminal (this will only take effect on the next reboot): nvram boot-args=cpus=1
  5. jeremy.king macrumors 603


    Jul 23, 2002
    Fuquay Varina, NC

    Just boot and hit delete/f5/f8 when the memory test starts and wait for BIOS to load :rolleyes:

    Macs have a similar interface called Open Firmware.

    Edit: No longer needed.

    Also, not sure what a second proc would have to do with a Java app, since if you did find any problems you would need to change the JVM.
  6. dalewalt thread starter macrumors newbie

    Apr 20, 2005

    thanks Robbie; doing it from the command line worked.

    king, our app is multi-threaded, and we've run into problems before running a multi-threaded Java app on a dual processor... disabling one processor fixes (masks :) the problem every time.

    thanks all

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