# Enabling 4GB RAM in XP SP2



## cjoyce1980 (Jul 17, 2007)

I've installed an extra 2GB of RAM in a DELL 745 to mae 4GB, but windows only sees 3GB and its says 4GB in the BIOS.

I've turned page file off and it only still sees 3GB.

How can i make it see this extra gig?


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## Wile E (Jul 17, 2007)

Short version = you can't. 

It has to do with the way the 32 bit OS addresses memory spaces.


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## HookeyStreet (Jul 17, 2007)

Wile E is correct, 4GB will never be 'shown' in Windows XP


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## theonetruewill (Jul 17, 2007)

Windows 32bit can only ever have just under 4GB in total memory. That includes virtual memory, RAM, and Gfx memory.


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## Wile E (Jul 17, 2007)

Yeah, you'll have to move to x64 Windows, to make use of it all.


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## mikey8684 (Jul 17, 2007)

I also have 4GB ram on XP MCE (32Bit) and VISTA Ultimate (64Bit) in a Dual boot and both say that I only have 3.25GB in the bios & system properties but in system information it says "Total Physical Memory = 4,096MB" ....

Does this mean that its like I only have 3GB installed or is coz of binary and such that it just cant be displayed in XP ... coz my Vista Ultimate says the same in the mentioned locations but its 64Bit, which I was under the impression that 64Bit could display 4GB or more.

OR AM I JUST CONFUSING THE HELL OUT OF MYSELF AND SHOULD JUST SHUT UP

But the only thing Im woried about is --- is it still performing with the full 4GB or not ...


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## tkpenalty (Jul 17, 2007)

Um guys...... ever heard of PAE?


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## ex_reven (Jul 17, 2007)

tkpenalty said:


> Um guys...... ever heard of PAE?



that still wont do a full 4 gig...more like 2.9


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## Wile E (Jul 17, 2007)

mikey8684 said:


> I also have 4GB ram on XP MCE (32Bit) and VISTA Ultimate (64Bit) in a Dual boot and both say that I only have 3.25GB in the bios & system properties but in system information it says "Total Physical Memory = 4,096MB" ....
> 
> Does this mean that its like I only have 3GB installed or is coz of binary and such that it just cant be displayed in XP ... coz my Vista Ultimate says the same in the mentioned locations but its 64Bit, which I was under the impression that 64Bit could display 4GB or more.
> 
> ...


Go thru your BIOS and look for a feature called Memory Hole Remap (or something similar), and enable it.



tkpenalty said:


> Um guys...... ever heard of PAE?


Still won't show the full 4GB. I get 3.25GB with /pae or /3GB enabled. (Note that the /3GB switch automatically enables PAE)


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## mikey8684 (Jul 17, 2007)

Mine must have PAE (Physical Address Extension) enable coz it says it under the hardware list in my computer properties and says I have 3.25GB....

But still does this mean my PC is only using what it is stating or is it actually using 4GB but because its 32Bit can only display 3.25GB ...


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## Wile E (Jul 17, 2007)

mikey8684 said:


> What is PAE ...


Physical Address Extension. It makes Windows address memory slightly differently. But do what I said in my post above yours first, then we'll talk PAE and /3GB. lol


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## ex_reven (Jul 17, 2007)

physical address extension
it maps more "areas" for windows to write to as memory


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## cjoyce1980 (Jul 17, 2007)

using /PAE i get 3.5GB now, that still better than having a whole gig wasting away

copy of my boot.ini file


```
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect /PAE
```


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## Wile E (Jul 17, 2007)

cjoyce1980 said:


> using /PAE i get 3.5GB now, that still better than having a whole gig wasting away
> 
> copy of my boot.ini file
> 
> ...


I suggest the /3GB switch. It limits the kernel to 1GB and allows the rest to programs. /PAE splits it down the middle. The kernel doesn't need that much ram.


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## cjoyce1980 (Jul 17, 2007)

Wile E said:


> I suggest the /3GB switch. It limits the kernel to 1GB and allows the rest to programs. /PAE splits it down the middle. The kernel doesn't need that much ram.



What is the difference?


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## Wile E (Jul 17, 2007)

cjoyce1980 said:


> What is the difference?


with just the PAE switch, the Windows kernel reserves 1.75GB of your 3.5GB all to itself. Programs can't access anymore than 1.75GB, in that config. 

If you use /3GB instead, the kernel only reserves 1GB, leaving 2.5GB for your programs to use.


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## EviLZeD (Jul 17, 2007)

usually for me xp 32bit picked up 3.25gb on my recent install its detected 3.5gb also vista 64bit  
has detected all the ram


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## cjoyce1980 (Jul 17, 2007)

Wile E said:


> with just the PAE switch, the Windows kernel reserves 1.75GB of your 3.5GB all to itself. Programs can't access anymore than 1.75GB, in that config.
> 
> If you use /3GB instead, the kernel only reserves 1GB, leaving 2.5GB for your programs to use.



so with this switch,  kernel gets 512mb and system gets 3GB? right


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## ex_reven (Jul 17, 2007)

cjoyce1980 said:


> so with this switch,  kernel gets 512mb and system gets 3GB? right



no. The kernel will still have 1 gig.
Ordinarily, without the switch the ram usage is split 50/50.
The 3gb switch just means that it will limit the kernel to 1 gig and give the remainder to applications etc.


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## cjoyce1980 (Jul 17, 2007)

ex_reven said:


> no. The kernel will still have 1 gig.
> Ordinarily, without the switch the ram usage is split 50/50.
> The 3gb switch just means that it will limit the kernel to 1 gig and give the remainder to applications etc.



let me get this right, so with page file off, 128mb video ram and 4gb of system ram i will have
1GB for kernel
2.75GB for system

or is it......

1GB for kernel
3GB for system


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## Wile E (Jul 17, 2007)

cjoyce1980 said:


> let me get this right, so with page file off, 128mb video ram and 4gb of system ram i will have
> 1GB for kernel
> 2.75GB for system
> 
> ...


1GB = kernel

The rest of what Windows sees of your ram = applications.

With out it, Windows splits the ram evenly between kernel and apps.

Note that applications CANNOT access the ram set aside for the kernel.


EDIT: Trust us, just add the /3GB switch to your boot.ini  It's just better. lol


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## cjoyce1980 (Jul 17, 2007)

cheers guys, many thanks


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## niko084 (Jul 17, 2007)

I wish windows xp would use ram like Windows Server os's.... 

Just use it to cache instead as an os...
Like see and use all 16 gigs and just cache multiple programs on boot including your os..


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## Was_ser (Nov 29, 2009)

Information for thinking:
http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm


Follow link, and you will see that 32-bit win will work with even 8GB. Don't be frauded by M$, but keep in mind about WGA, and othe validation tools after .

I know, that thread old, but i want to post that _technically_ x86 win will able to use all RAM


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## Zubasa (Nov 29, 2009)

Was_ser said:


> Information for thinking:
> http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm
> 
> 
> ...


Do you even understand why the 4GB limit is even there? 
Sure you can force windows to install under 8GB ram but it doesn't meant that the extra will get utlized like it is in X86-64.
Whats the point of seeing 8GB in windows if it cannot address that memeory for application use?

One thing you need to know is the OP is using Windows XP, it is not like Win Vista that is build upon a kernal similar to Win Server 2003 .


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## Wile E (Nov 29, 2009)

Was_ser said:


> Information for thinking:
> http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm
> 
> 
> ...



It may be able to see it, but it can't use it. It's a limitation of 32bit addressing, not an artificial limit. For the computer to address more in a 32bit OS or program, PAE needs to be used, which switches memory management to 64bit, in a sense. That incurs a loss of compute performance tho, so the benefits of more memory needs to outweigh the loss of computing power.


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## Zubasa (Nov 29, 2009)

Wile E said:


> It may be able to see it, but it can't use it. It's a limitation of 32bit addressing, not an artificial limit. For the computer to address more in a 32bit OS or program, PAE needs to be used, which switches memory management to 36bit, iirc. That incurs a loss of compute performance tho, so the benefits of more memory needs to outweigh the loss of computing power.


Exactly.
PAE allows the OS the adresss more memory, but whats the point if normal 32-bit applications cannot address the extra memory?


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## Completely Bonkers (Nov 29, 2009)

Zubasa said:


> PAE allows the OS the adresss more memory, but whats the point if normal 32-bit applications cannot address the extra memory?


1./ *EACH* 32-bit application gets it's 2GB/3GB memory allocation. Meaning that if you have more than 1 application running, there is a benefit. If you have only 1 application, then agreed, no benefit.

2./ RAMdisk. It can use the >4GB memory area


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## d3fct (Nov 30, 2009)

well i have 8 gigs of g.skill i benched it on x86 and 64 bit xp and windows 7 x86 and 64 bit, can u guess wich os won?
surprisingly enough, xp pro sp2 won x86.

i benched prime, super pi, and 3dmark06 on each install ,fresh install on raid 0 each time.

so i wouldnt worry to much about what shows up as your memory in windows.


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