Replacing RAM in PowerBook with lower latency SO-DIMMs

Discussion in 'Macintosh Computers' started by bradz_id, May 18, 2004.

  1. bradz_id macrumors member

    Nov 16, 2002
    Tasmania, Australia

    Corsair just released new XMS-2700LL SO-DIMMs for laptops with a CAS latency of 2. Apple's hardware documentation says that PowerBooks run at CL2.5. I am assuming that if I take out the CL2.5 RAM and replace it with CL2 RAM, it will run it on the new timings based on the SPD chip in the RAM. Am I right in saying that or is it locked to run at 2.5. Is there a firmware command to set RAM timings?
  2. saabmp3 macrumors 6502a

    Jul 22, 2002
    Tacoma, WA
    With my desktop you had to adjust a setting in the BIOS (equivalent of Firmware) to use the CAS 2 latency timing. I don't think this is going to improve your speed.

  3. Versello macrumors regular

    Nov 13, 2003
    Yeah, performance between 2 and 2.5 isn't noticeable.
  4. bradz_id thread starter macrumors member

    Nov 16, 2002
    Tasmania, Australia
    I have Corsair TWINX-3200LL in my PC and I want every bit of performance that I can get out of my laptop. Low latency made a difference in my PC and I would like to do the same in my laptop. What I want to know is if I buy CL2 RAM, Will it run at CL2?
  5. gekko513 macrumors 603


    Oct 16, 2003
    I don't think it's possible if you have a PowerBook with any non-removable RAM. Not sure though.
  6. hugemullens macrumors 6502a


    Dec 15, 2002
    Write this down, it is impossible for an apple product to run at different timings than what apple wants without SERIOUS firmware hacking. A CL of 2.5 is hardcoded into the firmware and no matter what ram you put in it, thats what it runs at. Desktop, laptop, if its a mac thats a fact. PC's are always usually hardcoded too in the realm of laptops, only maybe the new voodo, alienware and other niche laptops can adjust timings. But to answer the question, no timing advantage on the macintosh.
  7. Sun Baked macrumors G5

    Sun Baked

    May 19, 2002
    Sort of pointless to spend the money for expensive low latency PC2700 RAM, when the FSB of G4s saturates at slightly over 1 GB/s @ 166MHz.
  8. uncyherb macrumors newbie

    May 18, 2004
    Melbourne, Australia
    I've got a different, but somewhat related question...

    I'm picking up a new iBook G4 14 this week... So far I've been struggling to find a retail outlet with cheap ram of the PC2100 variety... no problem getting hold of 2700 though.

    Can I use the 333 stuff in a 266 locked machine. I know that I wont get any performance benifits... I'm just wondering if the faster ram will work or not?

    Thanks all.
  9. Rod Rod macrumors 68020

    Rod Rod

    Sep 21, 2003
    Las Vegas, NV
    yes, pc2700 ram will work fine in a pc2100 system. the ram will operate at the speed of your computer's ram spec (pc2100). if you can get it cheaper, do it. it works, and there are no performance advantages or disadvantages.


Share This Page