Weird!! G4 sees 566 mgz chip as 400!!

Discussion in 'PowerPC Macs' started by Retrosonic, Nov 25, 2009.

  1. Retrosonic macrumors regular

    May 13, 2009
    This is strange.....I have a G4 AGP Power Mac with the original 450 mgz Processor.

    I had read that if you upgrade the firmare to 4.2.8f1 (the last version available) that you could install a 566 mhz processor.

    So......I installed an 566 mhz processor board, part # 820-1175-A.

    The system boots fine and all that, but "About This Mac" sees the chip as a 400 mgz Processor!!!

    What is going on here? the system only running on 400 mhz??

    Any ideas?

    thanks for the help!
  2. iamcheerful macrumors 6502


    Oct 3, 2008
    was there even a 566MHz G4?
    or is this an over-clocking procedure?
  3. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    533 x 100/133 = 400

    The board is meant for a 133 Mhz bus machine.
  4. Retrosonic thread starter macrumors regular

    May 13, 2009
    566 Processor

    Thank you for the replys.


    Whats the best course of action here, leave the 566 processor board in, or put back the original 450 mgz processor?

    The reason I ask is because I'm thinking that some programs I might install will not install with the 450 chip in the G4, but they might work if the 566 chip is installed.

    your thoughts?

    thank you so much!

  5. OrangeSVTguy macrumors 601


    Sep 16, 2007
    Northeastern Ohio
    You can overclock those G4 processors. You can probably get around 50-75mhz with reliable results. I've done it to a few G4 Powermacs and even a G4 Mini :p.

    Just requires soldering/desoldering tiny resisters.
  6. Carolus Rex macrumors newbie

    Nov 26, 2009
    I would try and see how far it can be overclocked if I were you. It's not really an expensive pice of hardware that you have there, and you still have the other CPU if you need it, right?
    Perhaps this discussion could shed some additional light as well:
    There are listings available for multipliers and speeds that you can find with a search.
    As I see it, the processor should be able to handle quite an overclocking. It was built for 566?
  7. MacVidCards Suspended

    Nov 17, 2008
    Hollywood, CA
    In case I wasn't have a 533 Mhz processor ...when it runs on a 133 Mhz Bus.

    With the 100Mhz bus, speeds are decreased proportionately.

    If you or a friend can solder, use the chart on this page to try new speeds:

    Currently, it appears to be set for a 4X multiplier (4 x 100 Mhz = 400Mhz)

    If you were to up it to either a 5.5 multiplier or a 6.0 multiplier, you would end up with 550 or 600 Mhz. When I used to dabble in this stuff, I found 50 Mhz was almost always possible, so you could probably count on 550 but may or may not reach 600. Sometimes the cache would be first thing to not hook up, so you might reach 600Mhz but L2 cache won't work.

    A search of the part number yields a value of $25 or you have little to lose.
  8. Retrosonic thread starter macrumors regular

    May 13, 2009


    Thanks for the replies. I may just end up getting one of the Sonnet G4 processor upgrades. I'm wondering if they will support OSX 10.5.3 because thats what I have.......I think I read somewhere that they will not work with 10.5.

    thanks Retro Rick
  9. California macrumors 68040


    Aug 21, 2004
    I think they do work with leopard, just disable Dashboard.

    And max out ram.

    And get fastest hds you can get without the 128gb hard drive limit.

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