MBP's CAS latency support.

Discussion in 'MacBook Pro' started by lauph, Feb 29, 2008.

  1. lauph macrumors regular

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    30 mins from Cupertino
    #1
    The RAM buyer's guide says that if the CasLatency is faster than the hardware can support, then it will run at the machine's max supported speed.
    So.. the default apple rams, and many 667MHz rams sold are CL5, and theres this particular G.Skill ram that is rated for CL4, 4-4-4-12 for all timings.

    So does the MBP support the 4-4-4-12 settings? Anyone tried this yet?
     
  2. Lyshen macrumors 6502

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    #2
    I doubt it. Majority of laptops don't give users the option to tweak the bios settings in regards to ram setting. Even if you get Cas 4 ram, it'll most likely still run at cas 5.

    I haven't tried running it yet on the MBP, but there's a memtest program I normally run on PCs when I get new ram to check and make sure it is not bad ram. It is independent of the OS, runs as a bootable CD and tells the current settings on your ram.
     
  3. lauph thread starter macrumors regular

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    #3
    Cas Latency is auto detect or must it be set on bios/efi level manually?
     
  4. Lyshen macrumors 6502

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    #4
    On desktops its usually auto detect... but on laptops its normally just default set at 5 since there isn't much ram variation. Unless you have one of those gamer type desktop replacement laptops, usually there is no option to tweak the ram settings.

    Most laptop manufacturers of SR chipset expect the user to use 667MHz ram, and default is Cas 5 as the norm.
     
  5. Ant1-Hero macrumors regular

    Ant1-Hero

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    #5
    there must be a way to manually edit EFI, other then that load up windows xp and use CPU-Z
     
  6. CanadaRAM macrumors G5

    CanadaRAM

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    #6
    AFAIK It doesn't tell the actual speeds that are being used, it just reports what the SPD settings on the module have been programmed to respond with. Consequently, it won't tell you with any accuracy if the RAM is actually being run at "x" latency and "y" memory bus speed, only the RAM module's opinion "Yes I could possibly do that".
     
  7. lauph thread starter macrumors regular

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    #7
    So other than running benchmarks and see the difference in performance, there is no way to find out the Cas latency the system is running at?
     
  8. Lyshen macrumors 6502

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    #8
    Well as Ant1-Hero said earlier, if you load up Windows and use CPU-Z, one tab will tell you what your ram is currently running at and another tab will tel you what SPD your ram supports.
     
  9. lauph thread starter macrumors regular

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    #9
    Ok.. Now that there's the corsair's Mac Memory that has special SPD and claims a 100% compatible, 28% performance boost bla bla bla...

    I checked its website out, which says that its a cl4 with 4-4-4-12 timings.

    So... Does it mean the g skill's cl4 will work just as great?
     
  10. burningrave101 macrumors 6502

    Joined:
    Mar 4, 2008
    #10
    Whatever timings are programmed into the SPD of the memory is what it should be running at. If the SO-DIMM module advertised a 4-4-4-12 latency then that should be what it auto sets to. Laptops don't normally have overclocking options in the BIOS and memory manufacturers know this so they would be false marketing if their modules didn't run at those speeds in a current laptop. If you have any trouble getting them to detect at 4-4-4-12 then just contact G. Skill. That said it's not going to make any big difference in performance going from 4-4-4-12 to 5-5-5-15 at the same clock speed.
     
  11. zerohp macrumors member

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    Mar 6, 2008
    #11
    I ordered the G.skill memory on the report of someone else who said it was fine in a Penryn. I'll report back later once I get my new macbook pro up and running.
     
  12. scott9s macrumors member

    Joined:
    Feb 27, 2008
    #12
    I ordered the G.Skill Ram too.

    There should be no reason why the RAM won't work. The only thing I am wondering is if it works at the timing.

    I'll guess we'll have to see. I'll try to run some benchmarks when the memory and my 17" MBP arrive. (still waiting)

    One thing that I saw at mac-forums.com

    was that there are more apple benchmarks one might need to pass to be "mac memory". I wonder if it is anything like Windows Driver Certification. Yes, you give us some money, and sure we'll call your driver certified. :)
     

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