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3GB RAM Limit 1

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200820

IS-IT--Management
Nov 13, 2008
126
GB
I currently have 3GB RAM in my computer & was going to upgrade to 4GB. Will XP Pro recognise the new upgrade as I have read that there is a 3GB limit on some operating systems
 
If you're on 32 bit, don't bother. If you are on 64 bit, go for it.

"We can categorically state that we have not released man-eating badgers into the area" - Major Mike Shearer
 
I'm pretty sure it's 32-bit, is there a way to check this?


'Ver' at command prompt returns 'Microsoft Windows XP [Version 5.1.2600]'

Is there anyway at all that a 32bit system canrecognise 4GB RAM, I've seen a few articles about PAE (physical address extension) but not confident of how to implement it...
 
Start/Run then enter msinfo32.exe

It should show up under system type. I really wouldn't bother trying to add any more memory if it is 32.

"We can categorically state that we have not released man-eating badgers into the area" - Major Mike Shearer
 
Under system type it says 'X86-based PC'

Can I ask why you wouldn't recommend adding anymore because it is 32-bit?
 
PAE can only be taken advantage of if the software is written to take advantage of it. When you factor in all of your machine's memory, you won't get a performance boost.

"We can categorically state that we have not released man-eating badgers into the area" - Major Mike Shearer
 
Hey,

Windows XP 32 bit supports up to 4 GB. Windows takes this and splits it in half, using 2gb for apps, and 2gb for the kernel. If you add the /3g switch the boot.ini, then it uses 1gb for the kernel, and 3gb for apps.



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I take it this is done by control pane...system...advance...startup & recovery then edit the boot.ini file?

If so where abouts in the file does the switch need to be added?
 
Address allocation is going to take a big chunk of it all, plus you have to include video memory.

"We can categorically state that we have not released man-eating badgers into the area" - Major Mike Shearer
 
There are two separate items to be aware of here:

1) Physical RAM
2) Virtual Address Space

A 32-bit system is limited to 4GB of physical RAM and also 4GB of Virtual Address Space. Each byte of RAM needs a byte in the Virtual Address Space to be in use by the OS. The problem is that when you first turn on the computer (long before Windows loads), the hardware memory manager called MMIO (Memory-Mapped Input Output) reserves some of that Virtual Address Space. For example, the system buses such as PCI-E, AGP, Hypertransport, etc., all need address space to function. In newer systems it's not uncommon for the MMIO to grab 1GB or more, stealing address space away from system RAM. Different system configurations will vary. I've seen some computers show 3.25GB available in Windows when 4GB was installed. But even given this chance, is it worth putting another gig in just to get a small increase? The answer heavily depends on the type of apps you use.

So, this is not a limitation of the OS. Unfortunately, it's a shortage caused by other devices in the system that interact directly with the BIOS. Using switches like /PAE or /3GB won't likely help either and could actually hurt overall performance. The second thread I listed below explains that.

Here are some recent threads that address the issue:

thread602-1457391
thread602-1452884

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
[tab][navy]For posting policies, click [/navy]here.
 
I believe your version of BIOS holds the RAM limits.
Maybe a later version of BIOS may support a larger limit.

Just a guess.
 
3 > 4 isn't worth it. 2 > 4 is especially considering how cheap memory is.


 
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