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Using 4GB RAM on 32bit XP

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May 20, 2009 9:24:42 AM

I'm planning to upgrade my notebook's RAM to 2 * 2GB DDRII 800, i know not all of the 4GB memory could be utilized on my WinXP Professional 32bit system, I want to know if there is also any compatibility problems that may occur occassionally as a result of this upgrade?

(My notebook: Acer Aspire 5101, AMD MK36, ATI Radeon X1300)

Thanks in advance.

More about : 4gb ram 32bit

May 20, 2009 11:01:43 AM

U dont have to worry. It utilizes all the memory... The lesser memory where u c in your computer system properties.. that is display only... Cheers
a b } Memory
May 20, 2009 12:37:50 PM

witcherx said:
U dont have to worry. It utilizes all the memory... The lesser memory where u c in your computer system properties.. that is display only... Cheers



In a computer all bytes in the memory system need a unique name. This is called an address. For example, if you have 2 GB of main memory, then there are 2147483648 bytes of RAM in your machine, each of which require an address for the operating system to communicate to it. To give these all an address you need 31 bits to do it. Now, if/when you have 32 bits, you can name 4 GB (2 bytes to the 32nd power = 4GB).

This is why the total addressable space available in a 32 bit OS is 4GB – the OS runs out of addresses and cannot communicate/locate any more bytes of memory because of that.

You may think ”Hey, 4GB of address space… 4GB of RAM… What’s the problem” The problem is that memory isn’t the only thing needing an address. 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.


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.
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a b } Memory
May 20, 2009 12:38:47 PM

For the OP: As long as your motherboard supports that many DIMMS, you should have no problems running the modules themselves.
May 20, 2009 1:19:52 PM

Thanks a lot.

Another question: Is it true that DDRII 800 and DDRII 667 are made on the same production line and manufacturers just label those better-performing ones as 800 while marking those slightly inferior ones as 667 or 533?
a b } Memory
May 20, 2009 5:52:29 PM

I'm not involved in the manufacture, so I wouldn't be able to answer the specifics on that.

I *do* know that memory modules are tested and then "binned" according to their performance. Whether they are physically all the same or not? <shrug> Haven't had the time or inclination to study who's IC's of what design are being used in which maker's chips, and why...

From a pragmatic point of view - Unless you are overclocking and need the extra headroom to support higher Buss speeds, you should stick to the stock speed for your computer.
May 20, 2009 11:38:25 PM

I all i can say is scotteq...gave an excellent explanation of how it works with the addresses...couldn't put it any other way.
May 21, 2009 2:33:20 AM

Thanks very much.
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