iPhone OS 3.0 Memory Footprint

Discussion in 'iPhone' started by Eso, Mar 19, 2009.

  1. Eso macrumors 68000


    Aug 14, 2008
    Does anyone know how much RAM the OS itself uses? It would also be interesting to know how much standard apps like the iPod, Maps, Messaging, Mail, and Safari use on average.
  2. Eso thread starter macrumors 68000


    Aug 14, 2008

    I did some research and used the iStat app to measure the memory in use by the iPhone OS 2.2.1. I also found some information about system memory usage for OS X. Total memory is categorized as: wired, active, inactive, free. For the most part, memory that is actively being used falls under wired and active, and any memory available for applications is inactive or free. Wired is generally memory being used by the operating system. The point of this is to roughly get an idea about how capable the iPhone is at running apps simultaneously.

    First, I shut the iPhone down after installing iStat. I turned the iPhone on and immediately ran iStat from my homescreen:

    We can tell the total memory shown (96 MB) is not the actual amount of available memory (128 MB) so there is 32 MB of memory that is not being accounted for. It's probably being used by the OS, but anyways it isn't available for applications. The minimum amount of memory OS 2.2.1 uses is 56 MB. I have a first generation iPhone connected to WiFi with 1.73 GB free space, roughly 10 apps installed.

    Next, I started playing the iPod and left it playing in the background as I ran iStat again:

    There is now an additional 16 MB not being accounted for: free dropped by 25 MB, wired increased by 1 MB, active increased by 6 MB, inactive increased by 2 MB, and unaccounted increased by 16 MB. The net effect is the iPod is using 23 MB of memory to run in the background. There is just enough available memory left to run a second iPod in the background.

    Finally, I closed the iPod (via double home button tap -> close), opened (and closed) MacRumors.com/iPhone in safari, opened and closed the calender, and swiped between a few pages of apps and back:

    Available has dropped another 7 MB and unaccounted memory increased by 21 MB. Unfortunately I can not run iStat in parallel with another app.

    The iPhone OS 2.2.1 uses a minimum of 43.75% of the iPhone's RAM right from bootup. It averages around 60 MB of memory that is available for applications. It seems capable of running 2-3 modest applications at the same time.

    It would be nice if we could get some data from someone running 3.0 beta and from someone running 2.2.1 jailbroken and can run apps simultaneously for the following:
    1) Run iStat directly rebooting the iPhone.
    2) Run iStat after playing the iPod in the background (simultaneously if jailbroken).
    3) Run iStat after loading up MacRumors.com/iPhone in safari (as the only page, and simultaneous with the iPod and iStat if jailbroken).

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