Defrag: PAE, SkyDrive, VHDs, Arsenal of Halo 4

Play Defrag: PAE, SkyDrive, VHDs, Arsenal of Halo 4

The Discussion

  • User profile image

    It's worth clarifying the point on whether "your software needs to be built for PAE" and from previous comments on last weeks show:

    Firstly, let's be clear: AWE is not PAE. The first is about having more than 4GB of data in a process. The second is about having more than 4GB of RAM in a computer. ( You can use AWE without PAE, and you can use PAE without using AWE.

    Secondly, unlike AWE, PAE affects only things that look at physical addreses, i.e. some kernel mode drivers and the memory-management in the kernel itself - it doesn't affect normal user-mode programs. Consequently, to use physical memory above 4GB on a 32-bit system, only your kernel and some of your drivers need to be PAE aware - i.e. the ones that allocate physical addresses but foolishly assume that the physical addresses are 32-bit (physical addresses are actually 56 bit, just to be confusing). This truncation is the reason why 32-bit Windows chooses by default to ignore physical memory above 4GB and why it is disabled for Client SKUs.

    You also need to be running the PAE version of Windows Server. There's a flag in boot.ini (or bcdedit) called /PAE, but this has been enabled by default ever since XP SP2. On a side-note, PAE is a requirement of hardware-DEP, so if you have DEP enabled, PAE is enabled. It's also a requirement of Windows7, so if you're running Windows7, you've got PAE.

    Here's a good summary for the insanely few of you that actually care:

    Anyway, all that said, unless you've got a really good reason not to, you should be moving to a 64-bit OS. That way all of these complicated things just work and you don't have to think too hard about it.

  • User profile image

    I noticed you use Bing "MS Beta" Internal Preview. Any Wikileaks-style news on what new things are planned? We won't tell anyone.

  • User profile image

    Btw, here's a shout out for a new Windows Update optional extra that appeared this week without much fanfare, and that most people won't have noticed:

    It changes your desktop wallpaper every day to a random Bing wallpaper. To install, just open Windows Update and select it and install from the Optional Updates.

  • User profile image

    Here is a picture of the PAE patched Windows 7:

    Generic Comment Image


    as you can see it sees all my 8GB of RAM. Google for "wj32 PAE patch", this is the best patch. wj32 is the author of the open source Process Explorer clone called "Process Hacker".

    The PAE patch works, because the binaries are the same for all Editions (Client or server) and like already explained DEP/NX Bit requires PAE so most users already use PAE all the time (and Win8 requires it!!!). MS only added a licensing mechanism to limit some features (like VHD boot). The only real benefit from 64Bit Windows is to remove the 2GB virtual address space limit (when using 64bit apps) and this is why I installed the 64Bit Windows 7 Sp1 because xperfview and VS2010 often ran out of memory for me on a 32Bit windows. The patch is useful because of the missing direct upgrade from 32Bit Windows to 64Bit Windows. So you have a lot of work to reinstall everything and you have no real benefit because 64Bit uses 500MB more compared to 32Bit.

    [04:48] - VHD boot & Windows SKU's redux.

    again, stupid license policy which only allows VHD boot for Win7 Enterprise or Ultimate, all Server 2008R2 editions and all Embedded version (ThinPC, POSReady, Standard 7).

    If you spend some money you can try this 3rd party solution to also boot WinXP, Vista and Linux from a VHD:


  • User profile image

    One of my dev machines runs Windows 7 Professional and I am able to boot from VHD into Windows 8 Consumer Preview no problem.

    I followed the advice of Scott Hanselman in his excellent blog post and didn't hit a single issue. This definitely works on my machine, Windows 7 Professional 64-bit:

    The previous video was talking about booting into Windows 8 on a machine that already runs Windows 7, which will work (Win 7 Pro for me, Win8 CP on a VHD).

    But I don't believe you can boot Windows 7 from a VHD if you only have pro as stated in this video.

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