4 Gb Ram: Windows reads only 3 GB?

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I have a dual Xeon with 4 gb of Ram ,4 modules of 1 gb each of the same type,
they all work if installed 2 by 2 in any combination. The mainborad with 4
modules of 512 mb sees everything; I've tested just to check if there was
something wrong on it. If I install the 4 1 gb moduls I can't see more than 3
gb. Where's the trick?
 
I have a dual Xeon with 4 gb of Ram ,4 modules of 1 gb each of the same type,
they all work if installed 2 by 2 in any combination. The mainborad with 4
modules of 512 mb sees everything; I've tested just to check if there was
something wrong on it. If I install the 4 1 gb moduls I can't see more than 3
gb. Where's the trick?
Click to expand...

What does the motherboard vendor say?

Some motherboards, while they permit installation of 4 sticks of Memory,
they don't fully support it.

What motherboard? Have you checked to see if there is a BIOS update?
 
Hardware is ok I see all the memory during the boot of the machine, and if a
try a linux live cd, (knoppix) it's all there

"Leythos" ha scritto:
 
You need an OS that supports more than 4 GB. Windows XP 32 bit only supports
4 GB. Some of the address space is needed for the system. Depending on your
motherboard it will be hard to get Windows to show more than somewhere
around 3.25 GB. If you want to run Windows with more ram than that you'll
need to use a 64 bit version like XP 64 bit or Vista 64 bit. Make sure that
drivers are available for your hardware before you switch to a 64 bit
version of Windows. 32 bit drivers won't work in a 64 bit OS.
 
Do a Google search on boot.ini and you'll find info about switches needed
when memory is above 3Gb.
 
I have a dual Xeon with 4 gb of Ram ,4 modules of 1 gb each of the same type,
they all work if installed 2 by 2 in any combination. The mainborad with 4
modules of 512 mb sees everything; I've tested just to check if there was
something wrong on it. If I install the 4 1 gb moduls I can't see more than 3
gb. Where's the trick?
Click to expand...

32-bit OSes can't see the full 4gb because some of the space is used
for other purposes.
 
Do a Google search on boot.ini and you'll find info about switches needed
when memory is above 3Gb.
Click to expand...

Those switches won't help. They address the virtual memory. This is a physical memory
issue. As has been stated, the hardware takes some of the memory space (PCI devices, the
newest PCI is quite the memory gobbler and probably the main culprit). The only way to get
the memory back, as stated, is to run 64 bit XP (and that may not get it all back).
 
Mike said:
Those switches won't help. They address the virtual memory. This is a physical memory
issue. As has been stated, the hardware takes some of the memory space (PCI devices, the
newest PCI is quite the memory gobbler and probably the main culprit). The only way to get
the memory back, as stated, is to run 64 bit XP (and that may not get it all back).
Click to expand...

The switch (/3GB or something like that) does help some. IIRC, using that
switch makes ~3.2GB usable; better than 3, but still not the whole 4 yards.
 
Bob said:
The switch (/3GB or something like that) does help some. IIRC, using
that switch makes ~3.2GB usable; better than 3, but still not the
whole 4 yards.
Click to expand...

It gives applications 3 GB to work with but it does this by taking 1 GB from
the system. Only applications written to work with this will benefit at the
expense of slowing down some system functions. The only real benefit to the
/3 GB switch for most people is cosmetic, System Properties shows a bit more
RAM.
 
The switch (/3GB or something like that) does help some. IIRC, using that
switch makes ~3.2GB usable; better than 3, but still not the whole 4 yards.
Click to expand...

It makes 3GB useable by one program, otherwise the limit is 2GB.

I've got 4GB physical, 3.25GB available, no /3gb switch.
 
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