FSB on the MBP 17 = 800mhz.. so why the 667 ram?

Discussion in 'MacBook Pro' started by bbplayer5, Oct 30, 2007.

  1. bbplayer5 macrumors 68030

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    #1
    Is there 800mhz DDR you can throw into these?
     
  2. Eidorian macrumors Penryn

    Eidorian

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  3. rrijkers macrumors 6502

    rrijkers

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    #3
    Thats what i thought too, but i think it are 2 different things... :(
     
  4. Eidorian macrumors Penryn

    Eidorian

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    #4
    RAM speed can be independent of the front side bus speed.
     
  5. Eluzion macrumors 6502

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    #5
    Based on what I was told, the Santa Rose core doesn't run RAM at 800mhz frequency. The 800mhz advertised is the FSB, which is the northbridge connector with the CPU. So running DDR2 6400 RAM, it would still underclock to 667mhz.
     
  6. Eidorian macrumors Penryn

    Eidorian

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    #6
    That's right! :D
     
  7. Eluzion macrumors 6502

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    #7
    Must be a mobile CPU thing though because every CPU (AMD or Intel) I've used on a desktop runs a 1:1 ratio with the FSB. Either way, no biggy. MBP is still a beast. ;)
     
  8. Mindflux macrumors 68000

    Mindflux

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    #8

    You must not have been around a lot of desktops.

    I have a slew of 1200 Athlon's at the office that run at a 133Mhz multiplier for CPU clock frequency. The ram? DDR-2100 (266MHz)
     
  9. Eidorian macrumors Penryn

    Eidorian

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    #9
    133 MHz double pumped = 266 MHz

    Not in actual clock speed though. The RAM still runs at 133 MHz.
     
  10. Mindflux macrumors 68000

    Mindflux

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    #10
    Yes,but these Athlon FSB is 133, not 266 ;)
     
  11. Eidorian macrumors Penryn

    Eidorian

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    #11
    The RAM still runs at 133 MHz.
     
  12. TheStu macrumors 65816

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    #12
    That and more and more of the Intel chips that have the shiny new 1333MHz FSBs can run on 800MHz or faster DDR2 (though I think that the actually, the 1333 is DDR3 RAM... but whatever)
     
  13. Eidorian macrumors Penryn

    Eidorian

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    #13
    Yeah just thinking about it does give headaches when you now add DDR3 into the mix.

    DDR = Memory Clock * 2 (133 MHz = DDR-266 = PC 2100)
    DDR2 = Memory Clock * 4 (133 MHz = DDR2-533 = PC2 4200)
    DDR3 = Memory Clock * 8 (133 MHz = DDR3-1066 = PC3 8500)

    The 1,333 MHz front side bus would be 333 MHz * 4. (quad pumped)
     

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