New 24 iMac (2.8) RAM, fan speeds, temps

Discussion in 'iMac' started by stevol, May 15, 2008.

  1. stevol macrumors member

    Apr 20, 2008
    Sorry if these are old topics but here goes:

    1) I have 4 GB RAM and if I don't restart for a while, the free RAM gets less and less over a few hours even after quitting all programs. From about 3 GB free to 1 GB free, even though all programs have been officially "quitted". Is this just typical of Mac caching its RAM? Is there a benefit to periodically restarting for this reason alone? Or leave it and let the Mac figure out its RAM / cache situation on its own? Is this normal?

    2) Fan speeds using istat are basically fixed - they never seem to change even though temps rise significantly. Is this normal? CPU and Hard Drive fan at approx 1199 speed and optical drive at 699, all the time! Temps I don't think are astronomical compared to what I have seen on this board, but hard drive gets into the 50's Celsius, and Power Supply in the 70's (C). Shouldn't the fan speeds increase as temps go up? Or only at what Apple calls extreme temps? Is this normal? It's quiet, but I don't care if it's quiet if it doesn't work!

    Thanks for the input -- new 24" iMac, 2.8, 4 GB RAM (factory, don't worry, only $180 with educ discount). Love it otherwise so far.
  2. gehrbox macrumors 65816


    Jul 5, 2007
    Memory usage

    OS X likes to use whatever memory is available. When you quit a program some or all of it will remain in "inactive memory". If you notice after a reboot the first time you open a program takes longer then the next time you open it. This is because the whole program does not need to be loaded back into memory from the hard drive. This "caching" of programs and data in memory goes on until most of your memory is being utilized. This continues until you reboot.

    When all memory is used up and more is needed OS X handles it one of two ways. If you have inactive memory available it will purge the closed programs and data from inactive memory and free the memory as needed. If you have no inactive memory available to be purged, the system will swap out parts of active memory to hard disk to free space. This is called virtual memory. It works, but slows the system down because the hard disk is much slower to access then memory.

    If you take a look at the Activity Monitor application you will be able to see how your memory is being used. Just understand that it is normal for the Mac to utilize nearly all the memory it can find.
  3. eXan macrumors 601


    Jan 10, 2005
    1) its normal
    2) But it does work, so why worry?
  4. kryszrich macrumors member

    Nov 22, 2006
    check out this thread which I just posted yesterday..

    I recommend downloading the smcFancontrol program and upping the fan speed. in my opinion Apple doesn't have the minimum set high enough. There's no reason for the computer to be completely silent. I increased my fan speed by a 1/3 or so and it made a huge difference in temps and i can barely hear the fans.

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