ideal RAM memory allocation ?

Discussion in 'Parallels Desktop for Mac' started by yampi, Mar 16, 2007.

  1. yampi

    yampi

    Messages:
    19
    Hi all,
    I have 2 GB RAM in my Macbook Core 2 duo running Parallels to load Windows XP (gave up on Vista dream), what is the best RAM memory allocation?

    I mostly use Mac, can I adjust the RAM as needed for faster performance of running OS?
    thanks,
    SA

    BTW : what is coherence?:cool:
     
  2. dkp

    dkp

    Messages:
    1,367
    Start with 512 assigned to Windows and see now it goes. If more is needed it will become obvious. There will be times when more or less is appropriate depending on what you're doing both in Windows and in OS X.
     
  3. Eagle246

    Eagle246

    Messages:
    14
    I have 1Gb MB and I allocate a little under 500 to windows and that is usually sufficient.

    As for coherence, doenload the lastest version and try it out, basicly you be using both Win and Mac at the same time. Give it a go, its really cool.
     
  4. yampi

    yampi

    Messages:
    19
    Thanks, so it seems 512 should be adequate for windows, how do I activate coherence mode?
    thanks
     
  5. Eagle246

    Eagle246

    Messages:
    14
    Make sure you've got a recent build that includes coherence, then boot into windows and in the parallels View menu select Coherece or click the button with the four little windows [​IMG]
    to view your windows desktop in coherence mode use the "Show Desktop" button next to the start button.
    I would also reccomend either turning dock hiding on or moving either the dock or the start bar to one side of the screen.
     
  6. tomservo291

    tomservo291

    Messages:
    90
    I've found that with 2GB of ram, if you plan to do a lot of work in both operating systems that 728MB for Windows XP is just about perfect.

    OS X is a memory hog and will use as much as is free whenever it can... the more you can reserve for OS X the more responsive your system will be overall.

    I'm not saying that XP is "better" at memory management, but it doesn't try and eat it up as quickly. With 728MB i can run a few pretty large JVMs simeltaneously without slowdown (250MB or so each.)
     
  7. dkp

    dkp

    Messages:
    1,367
    Free memory is memory you have purchased that is doing no work. I wouldn't own an OS that left perfectly good ram lay around unused.
     
  8. tomservo291

    tomservo291

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    90
    Not to sound like a pest, but you can't just say "here.. I have 2GB of ram Firefox, use it all and startup as fast as possible." What happens if 2GB of ram has been allocated to firefox, mail and say.. itunes. Now i try to open a ridiculously large file in Photoshop; before photoshop can even begin... the os has a lot of work to do to determine what memory can be paged to disk, freed up, or used for what application.

    Now you've just gone and slowed down your whole system because you used all your huge amount of ram for 3 applications that didnt need more then 100mb each... The OS doesn't need to be over-conservative with RAM, but it certainly cant throw it around like its free.
     
  9. yampi

    yampi

    Messages:
    19
    Ok folks, I am not an expert user and as I said, mostly run Mac OSX for daily routine, and yes I intend to use all RAM purchased. Is it possible before each windows start up to increase memory for smother operation and then turn it back towards OSX as I return to the premium OS.:eek:
     
  10. pigwiggle

    pigwiggle

    Messages:
    34
    I have 2G on a MB, 2GHz core duo. I took the 1G allocated to the guest (XP) back to 512 and coherence is now much snappier.
     
  11. dotcomjunkie

    dotcomjunkie

    Messages:
    51
    Wow! I just reduced XP from 1024 to 512 mb and it is more responsive...hmmm - what is Parallels doing that would make XP more responsive with less RAM?

    Any thoughts on Vista allocation?
     
  12. pigwiggle

    pigwiggle

    Messages:
    34
    My guess, knowing nothing about the workings of parallels, windows, or OSX, is that the overhead associated with the virtualization isn't figured into the memory allocated for the virtual machine. That is handled by OSX, which in turn benefits from the extra free memory. Or not. But it's working for me.
     
  13. tomservo291

    tomservo291

    Messages:
    90
    Parallels running in OS X is doing all of the hardware emulation, giving OS X a healthy amount of RAM is going to increase performance of both OS X and XP
     
  14. VTMac

    VTMac

    Messages:
    340
    It amazes me that people continue to think more RAM for XP will make it run faster.
    It simply doesn't work that way. XP is in many respects an OSX application when running under Parallels. (I know that analogy isn't exact, but I'm simplifying here.) Would you expect taking 1G of RAM away from OSX to make your iTunes run faster? Probably not. So why on earth do people think it will make their XP run faster? The key is balance. You want to allocate the MINIMUM to your XP VM that will still provide good performance. In MOST cases that will be LESS than you would have on a physical XP machine. This is because of caching that is performed by Parallels that seems to compensate for less RAM. For example, I have an XP Laptop with 768M. I run my VM at 256M and for the same apps, my VM is almost always faster. Most people will find good results with a VM allocated between 256M and 512M. Those doing more MEMORY intensive things (there is a difference between the type of resources apps need) will naturally need to allocate more RAM.

    Also, XP has one of the WORST memory allocators on market. There is a reason that Windows Server 2003 and up use a different memory allocator. It's because XP stinks at memory allocation. OSX (or any *nix based OS) is much, much more efficient at managing memory than XP.
     
  15. dotcomjunkie

    dotcomjunkie

    Messages:
    51
    I think people in this thread are trying to find that balance.

    I found out rather quickly that more memory for the guest OS didn't necessarily make it run better. But as you said, there is a balance.

    So for XP - I will keep trying to find the best balance, 512 or 768, whatever.

    I don't know why you are "amazed" that people would think that more RAM to the guest OS would mean faster performance.

    More RAM to a guest OS DOES mean faster performance - to a point. That point where you start robbing Parallels of its ability to emulate the machine.
     
  16. dkp

    dkp

    Messages:
    1,367
    Perhaps we're not talking about it the same way. There's a decent discussion here: http://docs.info.apple.com/article.html?artnum=107918

    Solaris, for example, uses free memory to create psuedo disk space for /tmp and it hugely increases performance. Doing software compiles in /tmp are incredibly fast. If that memory is needed elsewhere it is quickly reallocated. If you looked at free mem on one of those systems and didn't understand what was going on you'd swear you needed more memory.
     
  17. yampi

    yampi

    Messages:
    19
    Thank you all, I think I do get a decent idea about how to manage my RAM now, after all running Internet explorer on Parallels should not take too much memory, I'll set it around 512 and adjust from that point,
    great forum!
    regards,
    SA :eek:
     
  18. yampi

    yampi

    Messages:
    19
    actually for my machine the sweet XP RAM is 712, everything running superbly
    thanks again,SA
    :)
     
  19. simplicity

    simplicity

    Messages:
    90
    Still, I would like to be able to adjust the RAM on the VM on the fly. VMWare workstation has an option like this.

    My use case is to use Windows XP VM for Office, VPN, and some other work things. 90% of the time 384MB is enough for that. Sometimes though I have to break out the ole' Visual Studio to do something. To keep the box from crawling, I need to shut down the VM, change the memory allocation and restart.

    Parallels could write a virtual memory driver for XP that would just use memory. For example, I allocate my VM a max memory of 1.2 GB. Then I set my active use to 384 MB, the virtual memory driver would eat the difference between the two so Windows thinks that it has 1.2 GB but most of it is in use. Later, as I am using the VM, I could 'free' some of that used memory for more intensive applications.

    That would be hecka sweet. Now go build it Parallels. :D :D :D
     
  20. Hugh Watkins

    Hugh Watkins

    Messages:
    943
    you are not yet a true macintosh power user
    all that is automated on the Mac

    just remember for Parallels small is beautiful and that 300 to 500 mb is enough

    10 years ago we used to allocate memory on the Mac but now it is automatic


    Hugh W
     

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