Windows XP does not recognize memory upgrade

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KrisR

I have upgraded my memory from 2GB to 4GB, using a set of matched 2x2GB
memory sticks.
During boot the BIOS correctly reports that installed memory is 4096 MB.

However, XP does not seem to recognize the memory upgrade.
The System Properties panel still reports "2.00 GB of RAM"
and the Task Manager says:
Physical Memory (K) 2096172

I realized that XP cannot get all of the 4GB, but I had expected to get at
least 3GB.

I have tried to set the /3GB boot parameter, but to no effect.

What is the problem?
 
KrisR said:
I have upgraded my memory from 2GB to 4GB, using a set of matched
2x2GB memory sticks.
During boot the BIOS correctly reports that installed memory is
4096 MB.

However, XP does not seem to recognize the memory upgrade.
The System Properties panel still reports "2.00 GB of RAM"
and the Task Manager says:
Physical Memory (K) 2096172

I realized that XP cannot get all of the 4GB, but I had expected to
get at least 3GB.

I have tried to set the /3GB boot parameter, but to no effect.

What is the problem?
Click to expand...

Windows XP what?
What motherboard (make and model) do you have? (If a laptop - what
make/model do you have?)
 
I'm running XP Pro 5.01.2600 SP3
Motherboard: Asus P5W DH Deluxe
Chipset: i975X
Processor: Core 2 Duo E6700 @ 2666 MHz
Graphics card: NVIDIA GeForce 8800 GT
Graphics card: NVIDIA GeForce 8600 GT

The motherboard manual says that 4GB may be installed with XP, but not all
will be
available for user space.
I realize that around 750MB out of the 4GB will be reserved for system
resources, and another 256MB may be taken by each of the graphics cards.
But that should still leave me with more than 2GB of user space?
I have seen reports by others who have successfully increased their user
space by upgrading memory to 4GB.
 
KrisR said:
I have upgraded my memory from 2GB to 4GB, using a set of matched 2x2GB
memory sticks.
During boot the BIOS correctly reports that installed memory is 4096 MB.

However, XP does not seem to recognize the memory upgrade.
The System Properties panel still reports "2.00 GB of RAM"
and the Task Manager says:
Physical Memory (K) 2096172

I realized that XP cannot get all of the 4GB, but I had expected to get at
least 3GB.

I have tried to set the /3GB boot parameter, but to no effect.

What is the problem?
Click to expand...

It is unlikely, but you could check boot.ini for a /maxmem=
setting. That can be used to limit the amount of physical
memory that Windows uses.

To test, I would download memtest86+ from memtest.org . The
screen should report the amount of memory the program is
testing. Memtest86+ is available to make a bootable floppy,
CD, or USB flash stick.

Here is a memtest86+ screen shot, while testing 512MB total memory.

http://www.memtest.org/pics/amd64-big.gif

You should let the program complete one pass of all its
tests, before pressing <esc> to reboot the computer. If
you encounter errors, you can try testing the sticks
one at a time, to make it easier to identify the
bad one.

If you have a bootable Linux LiveCD such as Knoppix or
Ubuntu, you could also try booting that as a test, and
query the available RAM in there.

Paul
 
Then are the particular modules supported by your mobo?
What are the modules?
Have you tried booting with a single stick, then swapping that stick in the
other connector?
Then repeating the process with the other single stick?
 
Check your BIOS to make sure the P5W memory remap feature is
NOT enabled. This for use with a 64 bit OS only. If you enable it
with a 32 bit OS, the useable memory will be restricted to 2GB.

Also, aren't your video cards 512MB, each?
 
Thank you for the various suggestions. They have helped in researching this
problem further and increasing my knowledge about what's going on. It is
certainly not a problem of malfunctioning hardware.

The basic problem is that of limited address space on a 32-bit computer.
In terms of the memory mapping - 2^32 = 4GB is the number of addresses
available. The system resources (System ROM, APIC(s), Integrated PCI devices
- such as network connectors and SCSI controllers, Graphics card and more)
have priority and get their addresses assigned first (otherwise they wont be
accessible) and the rest - Less than 4GB- is left for the user RAM.
Now its not that the remainder is used for anything\eaten up and so on - it
simply not mapped, which means that these memory locations have no addresses
that can be used to refer to them for read\write operations.

My calculation is approximately as follows:
For a start Windows XP always allocates around 750MB of the high end
addresses for non-memory use. If you have a lot of extra devices installed,
XP takes more.
In particular graphics cards are greedy. As I have two cards each with 512MB
of memory, 1G goes away right there. Given that I have many devices
installed, it is quite possible that all of my addresses above 2GB have been
taken.

I cannot be entirely sure of this though. I still cannot satifactorily
explain why XP reports *exactly* the same amount of user memory (2096172KB)
irrespective of installing 2GB or 4GB of physical memory. I should wish there
was a tool that could give me a complete memory map of XP. Anyone who knows
such a tool?

I need my graphics cards, so I shall just have to live with the limitation
of 2GB. That is not bad either :-) I also decided to keep all of my new
memory memory kit, even if only half is used, because this is faster memory
than I had before. I could have installed only one stick of 2GB, but the
benefit of dual channel is significant. As measured by PC Wizard, dual
channel gives 40% better memory performance and 6% global overall performance.

Again, thanks for the help!
 
I cannot be entirely sure of this though. I still cannot satifactorily
explain why XP reports *exactly* the same amount of user memory
(2096172KB)
irrespective of installing 2GB or 4GB of physical memory. I should wish
there
was a tool that could give me a complete memory map of XP. Anyone who
knows
such a tool?



"KrisR" wrote:
Click to expand...

Maybe you didn't see my post above. This is a symptom of enabling
the Memory remap feature in BIOS when using a 32 bit OS. The
memory remap is for a 64 bit OS only, with 4GB or above, and
moves the PCI hardware addressing above the highest physical
memory address. If you have a 32 bit OS, the hardware addressing
is moved downward to GB 3, so the system acts as though it only
has 2GB available.

Re a memory map tool, what memory would it map? There's no
point in mapping RAM as the contents are always changing and
don't correspond to application addresses. In regard to the virtual
addressing space, each running application has its own 4GB of virtual
address space, 2GB for the app and 2GB for XP. If you have three
instances of Internet Explorer running, each one would simultaneously
be using a lot of the same addresses for program code. However,
each would have its own virtual address space, so there would be no
conflict. The three IEs would be mapped form their virtual address space
into different locations in RAM, and these would be constantly changing
as dlls and data load and unload.
 
Ian,
Thank you for your clear explanations.
I did see your post earlier, however, I was unable to find any Memory remap
option in the BIOS. There is no reference to it in (even the most recent)
user manual and I cannot find any such parameter in my BIOS.

The manual just says:
"If you install Windows XP 32-bit version, the limitation of this OS version
is that it may reserve a certain amount of memory space for system devices.
We recommend that you install less than 3 GB sysem memory in you would like
to work under Windows XP 32-bit version. The excess memory installation will
not couse any usage problem, but it will not give users the benfit of
manipulation this excess memory space."

Do you know where this parameter is and how I can change it?

Maybe you are referring to a more recent BIOS version?
I have not updated my BIOS since I bought this board two years ago, never
felt the need for it, so I am still running the base version that came with
the board, v 1001.
 
Did you read my above post in this thread. It is your BIOS that is holding back.
Update it
 
What evidence do you have that this is indeed the remedy?
Is it a general hunch or do you have actual experience with this mobo?
 
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