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Windows XP and RAM 3.5GB+
Installed RAM : 4 GB but 2.96GB Usable......why?

I have a Macbook Pro with 4GB of installed RAM. I have installed Windows 7 on it which shows the usable memory as 2.74GB. Why is this? Don't tell me the 32 bit story; I program for a living. The maximum addressible memory on a 32 bit system is 4 GB not 3 GB.

Need proof? MSDN: Memory Limits for Windows Releases


Dont tell me the 32 bit story; I program for a living

It's the 32 bit story. Some things other than memory use the same address space, e.g. Memory mapped I/O.

Need proof?

  • 2
    Not to mention video memory. – Matt Ball Mar 2 '11 at 18:27
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    Definitely the 32 bit story. – Metril Mar 2 '11 at 18:48
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    +1. Just because you're a programmer doesn't mean you know everything. Other devices get access to the 4GB address space FIRST, RAM gets whatever is left. Install 64-bit Windows and watch what happens. – Shinrai Mar 2 '11 at 20:21

The biggest user of memory is normally the video card. If it has lots of memory, that memory is lost, as described in : The usable memory may be less than the installed memory on Windows 7-based computers

You may examine the memory usage on the computer by opening the Device Manager and under the View menu, choose "Resources by connection". Expand the Memory node and see if you can figure out what, if anything, is occupying the memory. In some cases, memory can be increased by disabling unused devices such as firewire.

Note: The so-called 3GB barrier is more like 4GB before it is eaten up by the devices.

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