Tom's Hardware > Forum > Motherboards & Memory > Memory > Whats the Max memory you can use on XP Pro 32
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billin30   08-07-2008 at 08:29:10 PM

I was just wondering what is the most memory you can use on xp pro 32. I have 4GB, but showing only 2.75 of usage. Is this accurate or is there something I can do to push that any further besides getting a new OS because I just dont care enough to go change something when it works just fine.

------------------------------ Intel Q6600 @ 3.0 GHz, Artic Cooling Freezer Pro 7, NZXT Apollo, OCZ GameXStream 850W PSU, 8800GTS 512 SLI, XFX 680i LT SLI, 4 GB OCZ SLI 5-5-5-15-2T, Seagate Barracuda 250 GB, WD 640 GB, Windows 7 Pro 64
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Scotteq   08-07-2008 at 08:33:29 PM
- 2 +

In 32 bit Windows operating systems, the total addressable space available is 4GB. If you install a total of 4GB worth of RAM, the system will detect/use/display less than 4GB of total memory because of address space allocation for other critical functions, such as:

- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- Configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices

Different onboard devices and different add-on cards (devices) will result of different total memory size. e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

This limitation applies to most chipsets & Windows XP/Vista 32-bit version operating systems. Again, this is a limitation of the Operating System not having enough address space to allocate to the system *and* the RAM. Not allocating address space to devices renders them inoperable. Not allocating addresses to RAM simply results in the unaddressed section not being used in an otherwise fully functional computer. Therefore the OS designers assign RAM last.

We can have long debates about mathematical fundamentals and discussions about why the original Windows designers couldn't allocate the full theoretical max of 36 bits of address space so that users today would be able to use more resource. But at the end of the day, the designers and engineers 'Didn't Then'. So we 'Can't Now'.


If you install a Windows operating system, and if more than 3GB memory is required for your system, then the below conditions must be met:

1. A memory controller which supports memory swap functionality is used. The latest chipsets like Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, AMD K8 and newer architectures can support the memory swap function.

2. Installation of Windows XP Pro X64 Ed. (64-bit), Windows Vista 64, or other OS which can provide more than 4GB worth of address space.



Note: According to the latest Change Log published by Microsoft, Windows Vista 32bit SP1 will display the installed amount of RAM. This is a display change only.

------------------------------ Being requested to remove my siggy implying some people here would receive greater personal benefit from a local Prostitute than from a new GPU in no way, shape, or form changes the aforementioned opinion.
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bf2142-rules-ok   08-07-2008 at 09:45:13 PM
- 0 +

I have 4gb of memory.Run Xp 32bit. I have a 8800gtx card that i see is mapped in 3 areas of 256mb of memory (doing a quick conversion of hex to dec of memory addresses found within resources in device manager) between the 3gb addresses and 4gb address. Therefore i take it that even though my 'system properties' tells me i have 3.25gb of memory i am not wasting my time having 4gb. And presumably this applies even more so to people who have for example 2 8800gtx in sli that have 1.5gb to map. I am afraid reading the 3gb issue on the web has so many conflicting views I am not sure whether i am coming or going!

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San Pedro   08-07-2008 at 09:56:19 PM
- 0 +

Here's the safe thing to do when building if you plan on getting 4+ gb of memory: Get a 64bit OS. If you have Vista you may be able to upgrade from 32bit to 64bit with little or no charge.

Message quoted 1 times
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billin30   08-07-2008 at 10:07:05 PM
- 0 +

My system properties shows that I have 2.75 GB of memory even though I have 2x2 GB sticks in my rig. Anything I can do to bump that number up a bit, because it looks like you have 3.25 and even that is an improvement. I have an SLI setup, which may cause the drop, but i just recently got the second card and it was 2.75 before and after installation.

Just curious and hoping to squeeze some more performance out

Message quoted 1 times
------------------------------ Intel Q6600 @ 3.0 GHz, Artic Cooling Freezer Pro 7, NZXT Apollo, OCZ GameXStream 850W PSU, 8800GTS 512 SLI, XFX 680i LT SLI, 4 GB OCZ SLI 5-5-5-15-2T, Seagate Barracuda 250 GB, WD 640 GB, Windows 7 Pro 64
 Reply to billin30
gamerk316   08-07-2008 at 10:14:43 PM
- 0 +

San Pedro wrote :

Here's the safe thing to do when building if you plan on getting 4+ gb of memory: Get a 64bit OS. If you have Vista you may be able to upgrade from 32bit to 64bit with little or no charge.



You can't upgrade from 32 to 64 bit; you need a fresh install

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Scotteq   08-07-2008 at 10:37:55 PM
- 0 +

billin30 wrote :

My system properties shows that I have 2.75 GB of memory even though I have 2x2 GB sticks in my rig. Anything I can do to bump that number up a bit, because it looks like you have 3.25 and even that is an improvement. I have an SLI setup, which may cause the drop, but i just recently got the second card and it was 2.75 before and after installation.

Just curious and hoping to squeeze some more performance out





If you must: You can go into the Bios and disable devices you don't think you will use in the hopes of freeing up more address space. Be advised you run a high liklihood of creating more - and more serious - issues than merely not being able to use all of your RAM.

In My Humble Opinion: Your choices at this point in time are to either accept the limitations of your current OS, or change to an operating system which can provide the necessary address space. That would be either XP64 or Vista 64, should you choose to remain a Windows user.

------------------------------ Being requested to remove my siggy implying some people here would receive greater personal benefit from a local Prostitute than from a new GPU in no way, shape, or form changes the aforementioned opinion.
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bf2142-rules-ok   08-07-2008 at 11:11:28 PM
- 0 +

And in my humble opinion - as you have gone to the trouble of buliding an SLI setup you must be a gamer so stay with XP, current games will give you no prob memory wise.

Message quoted 1 times
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Scotteq   08-08-2008 at 12:38:39 PM
- 0 +

bf2142-rules-ok wrote :

And in my humble opinion - as you have gone to the trouble of buliding an SLI setup you must be a gamer so stay with XP, current games will give you no prob memory wise.




SLI... Funny you mention that

Graphics cards are getting larger and larger in terms of memory mapped I/O - 512MB each for ones considered to be good performers on an enthusiast level. Go SLI/Crossfire? That's 1GB of address space taken up. Plus another 500~750MB for the computer itself. So you are now limited to about 2.25GB of memory. You want to pair "X2"s? Or 1GB 4870/GTX280's?? That's 2GB right there. Another 500~750MB for the system, and congrats!!! You *might* be able to boot...

You want Tri-Sli?? (3GB just for cards) or Quad Crossfire (4GB just for cards)?? You will have to use a 64 bit OS. No getting around it. A 32 bit OS just doesn't have the needed amount of address space to support it all.


And the growing complexity/hunger of games... CoH, Crysis, etc.... They will all consume 2GB of memory and more if it's there.


We aren't *quite* to that point yet. But a little simple math will tell you that a 64 bit OS is becoming an inevitability. Enthusiasts have already been bumping into 32 bit limits. Just ask the OP.


Message edited by Scotteq on 08-08-2008 at 03:25:40 PM
------------------------------ Being requested to remove my siggy implying some people here would receive greater personal benefit from a local Prostitute than from a new GPU in no way, shape, or form changes the aforementioned opinion.
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