G4 processor swap issues

Discussion in 'PowerPC Macs' started by TheMasin9, May 25, 2007.

  1. TheMasin9 macrumors 6502a

    TheMasin9

    Joined:
    Dec 22, 2004
    Location:
    Huber Heights, OH
    #1
    i have a couple of power mac g4s around the place and i recently swapped some of the processors around. I originaly had a pair of g4 466 "digital audio" machines and a g4 400 "sawtooth". After moving them around i end up with with a 466 "digital audio" a 533 "sawtooth" and a 350 "digital audio" can anyone tell me what is up with this. Does it have to do with the bus speed?
     
  2. crazzyeddie macrumors 68030

    crazzyeddie

    Joined:
    Dec 7, 2002
    Location:
    Florida, USA
    #2
    It has to do with the processor multiplier. Basically each CPU has a different "default" processor modifier, so when you move it to another machine (with a different multiplier configuration) it makes the CPU go faster/slower.
     
  3. Lovesong macrumors 65816

    Lovesong

    Joined:
    Sep 15, 2006
    Location:
    Stuck beween a rock and a hard place
    #3
    The sawtooth and DA did have different bus speeds- the DA was 133, while the sawtooth was 100. This should have nothing to do with the CPU swapping, but rather the type of RAM stick that might be useful to you.

    Now this is weird... One thing I was going to ask was whether you were sure that those CPUs were swappable. I know that they use different PSU adaptors- i.e. the sawtooths used the 20 pin adaptor, while the DAs had the weird 22 pin adaptor. Adding 50 Mhz from one chip to another makes no sense, and it might be that you've fried something.


    EDIT: Ah- crazyeddie got it. My bad.
     
  4. TheMasin9 thread starter macrumors 6502a

    TheMasin9

    Joined:
    Dec 22, 2004
    Location:
    Huber Heights, OH
    #4
    change processor multiplier

    is there any way to change this multiplier? especially on the 350 guy.
     
  5. TDM21 macrumors 6502a

    TDM21

    Joined:
    Jul 7, 2004
    #5
    I would guess the bus speed is the cause. The Sawtooth had a bus speed of 100MHz while the DA was 133MHz. The processors speed is determined by multiplying the bus speed.
     
  6. TheMasin9 thread starter macrumors 6502a

    TheMasin9

    Joined:
    Dec 22, 2004
    Location:
    Huber Heights, OH
    #6
    Processors swapped no problem, plug in plug out, they all have that ziff socket (i believe that is what its called).
     
  7. Kosh66 macrumors 6502

    Joined:
    Jul 15, 2004
    #7
    It has everything to do with the bus speed and the multiplier set on the motherboard or daughtercard. The G4 processor can run at half integer multiples of the bus speed. Some motherboards/daughtercards allow you to change the multiplier.
     
  8. SmurfBoxMasta macrumors 65816

    SmurfBoxMasta

    Joined:
    Nov 24, 2005
    Location:
    I'm only really here at night.
    #8
    uummm...........IIRC, the last mac to have mobo jumpers for the cpu was the B&W G3. Apple took them out to prevent overclocking :)

    But some aftermarket cpu cards do have jumpers on them even now :D

    And yes, it DOES have everything to do with the fsb speeds........
     
  9. drj434343 macrumors member

    drj434343

    Joined:
    Jan 11, 2006
    Location:
    Portland, OR
    #9
    I think we can do a little math to figure it out. Lets take the example of a processor swap between a 466 DA and a 400 Sawtooth.

    Sawtooth: 100Mhz bus x 4.0 multiplier = 400Mhz CPU
    DA: 133Mhz bus x 3.5 multiplier = 466Mhz CPU

    Now, a 100Mhz bus sawtooth G4 can't or won't operate at 133Mhz bus speeds. That means the DA must have clocked itself down to 100Mhz bus, but applied the original 3.5 multiplier. This would give you 350Mhz on the DA.

    The Sawtooth machine is more of a wonder. It appears it adjusted appropriately to the 133Mhz bus of the newer CPU, but applied its old multiplier as well. 133Mhz x 4.0 multiplier = 533 Mhz. What I don't understand is how the Sawtooth appears to operate at that bus, given the motherboard RAM speed limitations, etc. It could be a false finder reading, perhaps.
     
  10. ReanimationLP macrumors 68030

    ReanimationLP

    Joined:
    Jan 8, 2005
    Location:
    On the moon.
    #10
    I wish I had a couple Powermac G4s just lying around. :rolleyes:
     

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