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MMIO Error using 4GB RAM and /3GB Switch in WinXP SP2

Discussion in 'RivaTuner Advanced Discussion forum' started by desertjedi, Feb 18, 2008.

  1. desertjedi

    desertjedi Member Guru

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    I recently put an extra 2GB of RAM in my WinXP SP2 box to bring it up to 4GB. I then added the /3GB switch (or /PAE switch as it's known) so apps would be able to use up to 3GB of the total 4GB available.

    RT doesn't seem to like this. At first, I thought it was because I made this change after RT was installed but I'm getting the same error even on fresh installs of RT. The error is:
    [​IMG]If you can't see that graphic, it says:

    MMIO protection system failed to allocate protected MMIO range. MMIO protection has been forcibly disabled.

    It is strongly not recommended to start any applications equipped with PunkBuster system while running in unprotected mode!


    I currently have a dual-boot set up in the boot.ini...one with the /3GB switch and one without.

    I thought I would bring this to your attention.
     
  2. Unwinder

    Unwinder Moderator Staff Member

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    It is not "RT doesn't seem to like it". MMIO protection mode means that MMIO registers aperture will be located in kernel address space. This space is shared for all drivers installed and running in the system and you do can get out of memory depending on installed drivers or depending on used OS switches (which also affect amount of free kernel memory available to drivers).
    There is nothing that can be done if there is not enought kernel memory available for RT's MMIO range and MMIO protection mode won't be available in this case. Better spam nice guys from Evenbalance to fix the Punkbuster's virus styled memory scanner, probably they'll finally decide to fix it after almost a year of silence. I'm no longer going to do their job for free.
     
  3. pigmonkey

    pigmonkey New Member

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    Thank you so much for pointing that out!

    i had a crash during 3dmark06, due to this issue. i have foolishly disregarded the mmio notice, since i figured (foolishly) that it only concerns punkbuster and online gaming. the conflict was caused by the 3GB switch, and once i removed it 3dmark finished it's course.

    Thanks again,

    Pigmonkey.
     
  4. desertjedi

    desertjedi Member Guru

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    Pigmonkey, I have no "real" problems using the /3GB switch and RivaTuner. I just get the error message box displayed twice on my screen at boot-up.

    I may simply reinstall RT and say no to "MMIO" to prevent this. I can turn PB off when I play Vegas MP.

    There are many other apps that simply don't like the /3GB switch at all! GPU-Z is one of them.

    With 4GB installed and using the /3GB switch, there should be a 3GB/1GB split between apps and the kernal.

    With 2GB of RAM installed (and no switch, of course), apps get 1GB and the kernal gets 1GB so I don't see any real difference but I'm no expert on this.
     
    Last edited: Feb 21, 2008

  5. Unwinder

    Unwinder Moderator Staff Member

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    Wrong. Don't forget about virtual memory management. It doesn't matter how much memory do you have physically installed, without 3GB switch 2GB of address space is always available for any application and 2GB are reserved for kernel address space.
    With /3GB switch kernel space is forcibly reduced to 1GB, giving 3GB to user mode applications.
     
    Last edited: Feb 21, 2008
  6. desertjedi

    desertjedi Member Guru

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    Thanks for the clarfication. So you're saying that the /3GB switch, in effect, reduces maximum kernal usage to 1GB from 2GB?
     
  7. Unwinder

    Unwinder Moderator Staff Member

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    Correct.
     
  8. jabloomf

    jabloomf Master Guru

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    Forgive me, since I have been using Vista x64 for a while now, but user programs can only use up to 2GB RAM, unless they are compiled with the IMAGE_FILE_LARGE_ADDRESS_AWARE flag or the exe header is modified to add this flag with a program like CFF Explorer. One thing that I don't understand about 32 bit Windows is that it assigns memory addresses to hardware (like your graphics card) in the > 3GB range. In Vista x64, if you go into the CMOS setup and turn on the option that says something like "remap memory hole", you can use all 4GB of RAM without interfering with the memory addresses reserved for hardware devices.


    That is supposed to be so. Device driver's MMIO ranges are supposed to be in kernel address space and they are supposed to be invisible for user mode applications. User mode applications also map hardware to their user address spaces, but as we seen with Punkbuster, inaccurately coded memory scanner can easily crash the hardware while peeking in such ranges.

    My apologies, mate. I've erroneously edited your post instead of replying to it. Sorry.

    No problem. I put it back, now at least everything makes sense. Do I get a free copy of RT? ;)
     
    Last edited: Feb 23, 2008

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