XP Pro SP2 will not recognize all my RAM

By gxk ·
I have an ASUS motherboard P4P800E DELUXE. P4 3.0 Ghz. Max memory 4GB. I upgraded from 2GB to 4GB. Windows XP Pro (32bit) and my American Megatrends BIOS only recognize just under 3GB (2.8GB or so). Is there any way to get my BIOS and Windows to recognize all of it. I have a SAPHIRE RADEON 9600 (256MB) Graphics card which may take that much of the addressing but I still should be seeing over 3GB closer to 4GB no? Is there anyway to fix this without switching to a 64bit OS? Any help appreciated? All modules are the same and good. Belarc system analysis tells me there's a 1GB module in each socket but it too says the total is just under 3GB. I'm just about ready to just run it with 2GB until I'm ready to build a 64bit machine.

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I suspect you will find...

by OldER Mycroft In reply to XP Pro SP2 will not recog ...

That your endeavours to expand your memory resource has gone beyond what XP can handle.

Basically, you have too much RAM memory.

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Chip-Set Limitation

by TheChas In reply to XP Pro SP2 will not recog ...

While the 32 Bit version of XP does have a 3GB RAM limit, there is also a limit of around 3GB of addressable RAM for most 32 Bit motherboards.

From the P4P800 manual:
"When all four sockets are populated the 1GB DIMMs (total 4 GB), the system may detect only 3+GB (a little less than 4 GB) due to the Southbridge resource allocation."

While the chip-set can address 4 GB of RAM, the upper 700 MB to 1 GB must be "reserved" by the BIOS as this address space is used as temporary storage and pointers by the chip-set.

Intel has this covered in the design guides for the 865PE and other 32 bit chip-sets if you care to dig into the "why" further.


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by gxk In reply to Chip-Set Limitation

So 700MB of addressing is grabbed by the BIOS, and another 256MB by my graphics card. That's 956MB leaving 3.044. My BIOS detect something like 2.980. I may be a little off on that figure but it was just short of 3GB. Thanks for your response. It was very helpful.

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Just one thing that no one else has mentioned

by OH Smeg In reply to XP Pro SP2 will not recog ...

Where are you looking for RAM in Windows or BIOS?

If it's in Windows you are most likely not seeing it all as Windows can misreport this. For a proper answer you really need to look in BIOS for the amount of Installed RAM.


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by gxk In reply to Just one thing that no on ...

BIOS reads just under 3GB also which tells me it's probably my motherboard and I can't find any settings to change that. There doesn't seem to be a resolve for this besides starting from the ground up with a 64bit system.

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You could try a different M'Board or Flash the BIOS

by OH Smeg In reply to BIOS READS JUST UNDER 3GB

To a newer version if available.

However if you need to exceed the 4 GIG upper Limit that is built into the 32 Bit Systems you only have the option of moving to a 64 Bit OS but even that has it's own limitations as there are very few 64 Bit Windows Drivers available.

If you are considering this alliterative you should realise that Windows 64 Bit versions are only of any real use in Server Applications and are still fairly useless in a Desktop application where you need to install a lot of hardware like Printers, Scanners and the like.

Of course if you are looking at a 64 Bit Open Source alternative the story is completely different but there are not many willing to move away from their Windows Comfort Zone.


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BIOS are the latest

by gxk In reply to You could try a different ...

I have the latest BIOS and I may as well just wait another year or so before I swap MB's when I'm ready to make the Vista leap. I'll crawl around with my 2GB for a while.

Thanks much for great info.

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As long as your MB supports...

by NaughtyMonkey In reply to BIOS are the latest

all of the memory, then you could move to a 32 bit Windows 2003 Server OS. It can address 4 GB and with service packs can address more.

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Simple fix!

by bgalliford In reply to XP Pro SP2 will not recog ...

Simply put the /pae switch in your boot.ini

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/PAE switch did not work with XP Pro

by gxk In reply to Simple fix!

I did try the /PAE switch but to no avail. I have XP Professional. From everything I've read, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM and Windows Server 2003, Datacenter Edition supports 64 GB of physical RAM using the PAE feature but XP Pro, although no one states it's a no-go, it's never included with the above OS's.

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