CPU & RAM allocation to Windows 7

Discussion in 'Installation and Configuration' started by Skysurfer, Nov 4, 2011.

  1. I am writing this to help others and hopefully advance the knowledge base.

    This is my 4th week using a MBP 15 (early 2011) running Lion, Parallels 7 and Windows 7 when I started having problems playing WMV files in Windows Media Player. Parallels customer support suggested I change my allocation of CPUs and RAM to the virtual machine: CPUs went from 4 to 1; and RAM went from 4GB (of a total 8) to 3.

    The end result was that the WMV files played as they should, but my most critical Windows apps (Excel 2003, Outlook 2010, and Firefox) all developed serious lag issues. In fact, even dragging the cursor across the screen turned into a major chore. My MBP went from lightening fast performance to literally unworkable crawl.

    Bottom line: The next day, I adjusted CPUs to 3 and RAM to 4 and now my Windows apps work lightening fast again. I do not understand why Parallels recommends 1 CPU and 3GB RAM, but that is not a viable solution.

    Last edited: Nov 4, 2011
  2. Specimen

    Specimen Product Expert

    I hope you mean GB and not MB.

    I don't know how much RAM you got or how many cores your CPU has (no, I'm not going to google for your MBP model).
    But for a right balance between OSX and Windows the RAM assigned to a Windows 7 VM should be less than 50% of your physical RAM and at least 1 GB.

    The CPU setting you won't need to change from default as the threading usually adapts, but you should leave at least one core for OSX.

    My advice to anyone else is to not follow your advice, I'm sorry.
  3. Appreciate the input.


  4. I'm running my VM with 1.5 GB of Ram and just 1 core on an MBAir. It is running very nicely. Giving it 3 or even 4 GB sounds like a lot - Windows 7 isn't that terribly resource hungry.
  5. I was forced to make some teaks...turns out everything I need runs well except for multimedia. Apparently, Flash and Windows Media Player (both run on the Windows side) require less CPU & RAM allocations to run properly.

    So, it's a balancing act between maxing out the performance of key apps like Excel (for large economic models) and having the multimedia stuff run. Hopefully, I found a sweet spot with the last tweak: 2 CPUs and just a hair under 4GB RAM.


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