Enable 4GB of memory on Vista

Enable 4GB of memory on Vista
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Four Gigabytes is a lot of RAM for a workstation or gaming machine, but the industry has pretty much forced us into using this much (especially if you’re a heavy user of Virtual PC).  Most applications today are 32-bit and only address 2GB of RAM at a time (like Photoshop), but we need more memory for all the other running goodies that are memory-starved.  Even though Vista runs on 1GB of RAM, 2GB is alot better, and 4GB will unleash its potential.

Unfortunately, users of the 32-bit flavors of Vista have to run through some hoops to see all of the new RAM they’ve upgraded to.  Even then, they may not see all of the RAM available because of various hardware issues.  This article addresses various methods so you can utilize that massive amount of memory.

All 32-bit Operating Systems can only physically address 4 gigabytes of RAM, due to the math involved (232 = 4,294,967,296).  Depending on your hardware, Vista may only see 3GB or 3.5GB of the total RAM installed, because there are some devices that are memory mapped.  The most common culpret of this type of device is a video card, which can use up to 512MB of memory for mapping.

Enable PAE mode
You can tweak Vista’s core to add another 4-bits of addressing capability, but you must have a 64-bit capable processor (pretty much any processor made within the past two years like Intel’s Core 2 Duo or AMD’s Athlon 64).  Even though the math works out to address way more than 4GB (236 = 68,719,476,736), the operating system still has a cap (Windows Server can address anywhere from 8GB to 128GB depending on the flavor).

To force this new addressing method, you have to tell Vista to boot using this new parameter.  Vista no longer uses a BOOT.INI file as previous versions of Windows did, so you must modify the boot file using a built-in Vista tool called BCDedit.

  1. Open a command prompt (Press Window key + R to open the Run dialog, and then type cmd).
  2. Press Ctrl + Shift + Enter to execute (this allows you to run cmd in administrative mode if you haven’t already setup up a permanent admin mode).
  3. Type BCDedit /set PAE forceenable.

This PAE flag (Physical Address Extension) tells the Vista core to use an additional 4 bits of addressing, which in theory allows the OS to see all of the RAM you have available.  We’re not out of the woods yet, because once you reboot you may find that Vista still doesn’t see all of your RAM.  You can turn PAE off again by typing BCDedit /set PAE forcedisable or BCDedit /set PAE default.

Enable DEP mode
Also note that using PAE forces Vista to run theoretically slower, so you need to disable this feature if you go back to a lower amount of RAM.  Vista runs slower with PAE because of the new page-translation system being used.  By default Vista uses 2 cycles to address memory, and will use 3 when Physicall Address Extension is enabled.  PAE also supports advanced procesor features such as Data Execution Prevention (no execute), Non-Uniform Memory Architecture (NUMA), and hot-add memory.  PAE is automatically disabled when DEP (Data Execution Prevention) is disabled, so you must force PAE when DEP is disabled by running BCDedit again:

  1. Open a command prompt (Press Window key + R to open the Run dialog, and then type cmd).
  2. Press Ctrl + Shift + Enter to execute (this allows you to run cmd in administrative mode if you haven’t already setup up a permanent admin mode).
  3. Type BCDedit /set nx AlwaysOff
  4. Type BCDedit /set pae ForceEnable

You can disable DEP by typing BCDedit /set nx AlwaysOn

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53 Comments

  1. El Gaijin says:

    There is no way to use more than 4Gigs on Vista 32bit. I have tried everything, all kind of setting PAE etc. The best approach was using Win 2008 Server kernel, but with this you need the Win 2008 Server license + Media Center wouldn't work.
    The only solution, get all 64bit compatible hardware and then get Vista 64bit. No way around.

  2. Rick says:

    well i have good news this actually has boosted memory usage and has stabilized my system. with fingers crossed i rebooted, and it actually worked it took a little time, like a couple minutes but its a lot better tnx!

  3. Geoff Chappell says:

    If you have exactly 4GB of RAM, then depending on your other hardware and configuration, 64-bit Windows may not see any more RAM than does 32-bit Windows. Moreover, since 64-bit code is bigger, what memory it does see, it won't use as efficiently. And there is still the problem of being directed to 64 bits by a fake limit.

  4. Sam Ostroff says:

    If you have a retail version (non-OEM, that is) of Vista, you can get a free 64 bit disc from Microsoft. Shipping is ten bucks, but it's any easier workaround to 4+ gb. Search the msft site for 64 bit upgrade.

  5. Geoff Chappell says:

    Enabling PAE will not by itself let 32-bit Vista see any memory above 4GB. The code is there for using memory above 4GB, but you are not licensed to use it. For details, see my article http: http://www.geoffchappell.com notes windows license memory.htm.

  6. Nik says:

    You can use Windows 7 beta 64bit

  7. Hoan Le says:

    Vista SP1 will recognize 4GB. However, it won't operate with 4GB. Just use msinfo32 and you will see that the total physical memory still reports the number of ~3.3 – 3.6GB RAM.
    To make it works with >3GB RAM, the only way is to use 64bit OS.

  8. Whazza says:

    Strangely enough, doesn't work for me…

  9. Dan says:

    Really works and works well. Just gutted my computer and replaced everything. Got 4gb of memory, entered the command prompt entered the code and man did it take off…Love it

  10. mynamesux says:

    tested it on windows 7 7260.. no effect

  11. Dan says:

    I tried entering the bcdedit set pae forceenable command and my computer tells me that "access is denied". I'm the administrator, why can't I do it?

  12. ichae says:

    WARNING!!! If you are using BitLocker, Before using BCDEDIT make sure you have your bitlocker key on a USB external flash drive that you have handy or you will be unable to boot!

  13. dayle says:

    I have exactly 4gb ram 2 modules of the same manafacturer and same speed 667 mhz 2 gigs each. my mobo supports 4 gigs and bios reports it accuratelt as well, but when windows starts i get a BSOD, even using this tutorial still gets me a BSOD when 4gb is attached.

  14. Chris Bowling says:

    Hey Alan M.
    I followed your instructions as listed above and nothing happened. My computer(Vista Home Premium 32bit) does not recognize any additional RAM.
    Then I set the PAE back to default to get back where I started. Now, however, Internet Explorer will not run. It says to set the DEP settings but it won't let me. Says I'm not an administrator, but I am! PLEASE, can you help?
    Thanks,
    Chris B.

    • Greg M says:

      Chris B. I had the same problem with access, if you boot in safe mode (F8 at startup) then log in normal you can access BCDEdit through the start menu or C prompt

  15. Matthew says:

    Sadly this doesn't work at all for me… My system could easily run 64 bit windows which sadly looks like the only way I'll get my 4 gigs of RAM to work

  16. David says:

    A 32-bit OS can only assign 4GB of address space. If you have 4GB of RAM, you're trying to have your computer use all available addresses on RAM, which would mean that nothing else in your system could work. Instead of letting this happen, the 32 bit OS will use the address space for devices and then assign what's left over to your RAM.

    If you have 4GB of RAM on a 32-bit OS, the more memory used by your devices, the less address space available for RAM. A 512MB video card gives you a max of 3.5GB available for your RAM, because there is 1GB less of address space available.

  17. GEN-MIT says:

    Please delete this post. It returns atop of google search result for Ɗgb on vista'. Not only does it not work as intend on any machine my collegues and I have tried (6 different setups) but it also reduce 5 out of 6 machines memory to 2.8gb, instead of 4gb.

  18. Phana says:

    I have found something like the above guideline in a forum. And I haven't tried out yet..cuz afraid of I can't go back. Then I check out in google and see this. I also have Vista sp1 ultimate with 4gb of Ram. In the welcome senter, in the basic information I see the Ram status is 4GB. But if I look in DirectX it show only 3326MB something like that. Does this mean I have to follow this guideline..?

  19. Dan says:

    This simply doesn't work. To get support for more than 4GB RAM, you either need to get any 64-bit version of Windows or Windows Server 2003 2008 32-bit.No matter what you do, Vista 32-bit will not address more than 4GB RAM.

  20. Suhail Salman says:

    I should read the comments before the article :). The system is now reporting 3.55GB.
    anyone figured how to get this back?

  21. Guido says:

    i have Vista Ultimate sp1 32 bits with 4 gb ram. i DISABLE in bios on-board card video cause i have an off board one with 512 mb…. otherwise all of 4gb should be available…justa an on board audio is enable.. my precessor is a Phenom Triple Core 8400 2.1 ghz .. and i havee memory remmaping at bios… but no more than 3gb is recognize by Vista….. just in BIOS appear 4 GB but not in Vista…. any clue for me:??? thnaks in advance and hugs from Brazil

  22. walter says:

    Help i can't use internet explorer anymore because dep is turned of can't be turned on again …

  23. a different matt says:

    Question–does it help if a memory-intensive device (like a video card) has its own memory? I just ordered a 32-bit Vista SP1 machine with a 512 MB video card and 4 GB of RAM intuitively, it seems that a card like that would defer to its own memory and stay out of system memory, so I wouldn't have to enable PAE. Anyone have any thoughts?

  24. darren says:

    This guide didn't work after the PAE DEP step. Although I thought I'd give it a shot it didn't work. I'm not complaining though because it's still running fine.

  25. Ricky says:

    @ BRAM I also have the same problem.. instead of getting 3.55 GB i know have 2558 MB thanks to DEP and PAE enabling and stuff.

    Horrible Guide. F++

    • Alan says:

      Please note that your mileage may vary depending on your motherboard, chipset, and other factors. If you got bad results, then don't blame this guide, blame your chipset. The only sure-fire way to enable 4GB or more is to use a 64-bit OS and modern chipset.

      Ricky: what is your hardware configuration?

  26. Matt says:

    Interestingly, I installed Vista Ultimate 32bit SP1 on my machine, and system properties reports all 4 GB of ram…. XP only reported 2.99GB. Any explanation for this?

  27. Bram says:

    Interestingly enough I tried the baove solution because my Vista Home premium was only reporting 3.5 GB of RAM. After following the above it now reports 2.99 to all apps although the 4 Gig shows in the system properties. I disabled both DEP and PAE and cannot get the RAM back that I was using for process before…. any suggections?

  28. Adam says:

    Vista SP1 is smart enough to detect that you have 4gb installed, however, it can not use it all, take a look at your task manager (pres ctrl + alt + delete) and under the performance tab, you'll see a field under physical memory called, total, this field is how much ram your os has access to.

  29. Kristof 070 says:

    Yeah , this realy works . i am now using 6 GB RAM , because the page file ( by me ) is 6373 MB .

  30. drew says:

    well, my HP notebook only has 3GB, so Vista in theory should not have been different by enabling PAE, but i enabled it through Ultimate Windows Tweaker, and now the thing boots and runs like a demon!!!!!!!

  31. Giovanni says:

    I HAD TO FILL IN THE SHELL:BCDedit set PAE forceenable and all other possibility,but the windows say me :denied access,what can I do?thanks

  32. joseph tran says:

    Just wanted to thank you this worked os see 4gig taskmanager see 3gig http: support.microsoft.com kb 946003 explain where the one gig went to the graphics which can bee see on Performance Information and Tools on view and print details.

  33. shocked says:

    i'm shocked at the level of ignorance people have when it comes to extended memory switches. Microsoft disabled these features in none server OS for a reason. 32bit apps can only address 32bit worth of memory unless they are coded for PAE. for example SQL server is coded to use PAE but your average game isn't. If you need more than 4gb of ram just go buy a 64bit OS

  34. johnny says:

    this is what i run
    System NameTURKISHROYAL-PC
    System ManufacturerHewlett-Packard
    System ModelHP Pavilion dv7 Notebook PC
    System TypeX86-based PC
    ProcessorIntel(R) Core(TM)2 Quad CPU Q9000 @ 2.00GHz, 2001 Mhz, 4 Core(s), 4 Logical Processor(s)

  35. turkishroyal says:

    this thing works

  36. turkishroyal says:

    After running the command i rebooted,fine, everything seems t run like 3 times faster then it used to, its kinda scary cause i dont want it to fry.
    However, it does not show the total 6 gigs of ram installed, it still shows 3gigs. i didnt do the second step cause i dont know what it is. internet is faster so is restart and boot up by 5 times. Are these things normal?

  37. Siegfried says:

    you FORGET to mention the side effect of these method!!! this is crap!! totally CRAP!!! FK!! now my vista have its WINDOWS AUDIO not working!!! asshls!!

  38. Cryodragon says:

    I have 4GB of Kingston PC 2700 184 pin Dual Rank RAM and Vista 64 Bit SP2. RAM is indicated in BIOs and In Vista, but after about 5 Minutes system will crash and shut down. Is This A Graphics card problem (VisionTek ATI Radeon 3650 1GB Card) or a OS problem? or a MOBO Problem (Abit UL-8) ( CPU Athlon 64 )? The System is 64 bit dedicated.

  39. csd says:

    Good article but missing some essential info: setting pae will ONLY work if your processor, chipset and BIOS support >4GB memory addressing. You need to check your system specs …

  40. Arnon says:

    I entered to commands as explained, they were all executed successfully.
    But, when I open the Windows Task Manager, it still shows only 3 GB (The Vista does find the 4 GB in the computer properties). Should I see something else in the Task Manager ?

  41. forsamori says:

    Apparently Vista Service Pack 1 enabled Vista to use 4GB. I have just upgraded my PC's memory to 4GB from 3GB. Vista recognises it being 4GB in the machine on system properties yet refuses to use anything other than 3B of it. Whats going on?

    • Alan says:

      @forsamori: The short answer is yes, you will probably not be able to use > 3.5GB of RAM in Vista 32-bit. There are hacks that require using a Server 2008 core, but the safe short answer is: 4GB of RAM or greater should use 64-bit OS.

  42. etherrealryan says:

    this is bulls***,whoever post (how to get 4gb ram in vista 32bit) don't know what he's doing,you won't get 4gb ram in vista 32bit,you need vista 64bit ,don't try this settings because it make your computer run slower and make some programs not working….get windows vista 64 bit.

  43. stuart08 says:

    I was planning to upgrade my RAM from 2gb to 4gb. I use Vista 32 bit OS. But what I get from reading the above comments is that vista 32 bit will not recognise all 4Gb. So does it mean that in 32 bit OS we cannot have >3Gb RAM?

  44. Bob VanDyk says:

    To boot the system and utilize PAE memory, the PAE switch must be added to the corresponding entry in the Boot.ini file. If a problem should arise, Safe Mode may be used, which causes the system to boot using the normal kernel (support for only 4 GB of RAM) even if the PAE switch is part of the Boot.ini file.

  45. Bob Vandyk says:

    Presence of the NOEXECUTE switch on a system with a processor that supports hardware-enforced DEP implies the PAE switch. If the system processor is capable of hardware-enforced DEP and the NOEXECUTE switch is not present in the boot entry, Windows assumes NOEXECUTE=optin by default & enables PAE mode.

  46. Dan says:

    Mine has worked well over a year now have no complaints.

  47. yart diskang says:

    i`ve tried your way… still the same

  48. Brandon says:

    I built my computer in 2007 and I have been trying to find a way to use all my ram without spending another $400 bucks for Windows 7. This did not increase my RAM usage at all. Windows still reports that I have 2.8 GB RAM available, which is a lot to lose out of 4 GB.

  49. Acer Netbook says:

    Why are people still hammering on about this? Don't most PCs that come with 4GB of RAM have Windows 7 64-bit? I have an Acer Netbook that only has 3.7GB of RAM and it has 64-bit version of Windows.

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