Virtual RAM using a SSD almost as fast as actual RAM??

Discussion in 'MacBook Air' started by Luba, Oct 30, 2010.

  1. Luba macrumors 6502a

    Luba

    Joined:
    Apr 22, 2009
    #1
    The most demanding thing I would do with a new Air is watch videos, while having 5 windows open, while also running Office. Would 2GB be enough? And if it isn't just wondering when the MBA accesses more RAM virtually using the SSD how slow would it be? Half the speed of actual real RAM? A quarter? Or maybe it would be almost as fast as real RAM??
     
  2. admanimal macrumors 68040

    Joined:
    Apr 22, 2005
    #2
    SSDs can read/write at a couple hundred MB/s (at best). RAM can be read/written at several GB/s. That's an order of magnitude (i.e. 10x) difference at least.
     
  3. elwood58 macrumors member

    Joined:
    Oct 26, 2010
    Location:
    California
    #3
    Much slower than RAM, but faster than a spinning HDD.
     
  4. CaoCao macrumors 6502a

    Joined:
    Jul 27, 2010
    #4
    The SSD operates has 1000 times the latency of RAM.
    The SSD is fast enough that when using word the difference is imperceptible
     
  5. WardC macrumors 68030

    WardC

    Joined:
    Oct 17, 2007
    Location:
    Fort Worth, TX
    #5
    RAM will be faster than the SSD, but you can cut it with the SSD if you need to. If you need keep 20 heavy apps open at once and need to switch between them in half the blink of an eye, exchanging heavy data between apps, and don't like to quit apps and boot them again, then the extra RAM will give you an advantage, it will be much faster than VM on the SSD. There is an another thread about this called "2GB or 4GB dilemma" read up on it.
     
  6. fyrefly macrumors 6502a

    Joined:
    Jun 27, 2004
    #6
    BareFeats did a good piece on this... and no, the SSD will not make PAge-Outs and Virtual Memory use a non-issue.

    BF says: "Does the flash storage making virtual memory (VM) paging a non-issue? No, because real memory is 20 times faster than flash storage. The MacBook Air's RAM transfers at 4000MB/s according to our memory stress tests. The flash storage transfers at 200MB/s."
     
  7. DannySmurf macrumors 6502a

    Joined:
    Jul 7, 2005
    #7
    For the casual use that the OP mentioned, 200MB/s is quite sufficient.
     
  8. WardC macrumors 68030

    WardC

    Joined:
    Oct 17, 2007
    Location:
    Fort Worth, TX
    #8
    The real transfer speed of the internal SSD is about 150MB/sec sustained. So to load a 300MB program into RAM would take 2 seconds. Loading it into RAM would take 0.075 seconds. So I would say that the RAM route is alot faster if you are running a great deal of RAM-heavy apps concurrently. You will notice faster loading of apps and switching between apps.
     

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