Windows x64 and 4gigs of ram showing only 3 gigs

[Ulrick28]

I am running an Intel P4 660 With 4 gigs of DDR2 533 memory. The problem I am having is that Windows x64 is showing 3 gigs. I thought one of the advantages of windows 64 was the ability to have more ram available (I realize that in Windows XP Pro 32bit a lot of hardare assigned itself between the 3 gig and 4 gig space). Is this still true for XP x64 as well?

It's painful knowing I have a full gig of ram I can't use....

[bledd]

which motherboard do you have?

some only support 3gb> when you use ECC ram..

[Weed]

on some mainboards u need to active 4gb support in bios

for example asus a8n-sli

[Jito463]

Have you checked the manual for your MoBo to verify it supports more than 3GB of RAM? Also, I know some Intel boards had issues with more then 3 sticks (even if all sticks are only 512MB). Remember though, the 64-bit extensons on the Intel's were cobbled together at the last minute. This isn't a ding at Intel, but a statement of fact. They were about to get left in the dust by AMD and this was their interim release until they could produce a true x64 compatible CPU. This could pertain to your issue as well.

[Jotnar]

You might want to check and see if there is a BIOS update for your board (try calling if you have to). My 8 CPU Iwill system wouldn't even let me install x64 Windows until I got the latest BIOS from them (they even said they had tested installing x64 Windows...utter BS as the Final, RC and Beta installs all failed at the same point). Now its happily chugging along under Windows Server 2003 Enterprise x64 and seeing all of its 16Gb of memory.

Cheers

[Jazkal]

Some motherboard take memory and dedicate it for the PCI bus. A Dell 2850 with 4 gigs of ram will only show 3 gigs in Windows. A Dell 2650 with 4 gigs of ram, shows 3.5gigs in windows. This is a "feature", not a bug, or so Dell says.

Looking into it, it seems that most Motherboards companys design them this way. I think that it matters how much "stuff" they throw on the motherboard.

You can get around this with a /PAE switch, but Microsoft doesn't suggest using it on a production system, something about stability.

[buletov]

and where do you apply this switch? in boot.ini or?

[thomasd]

Try adding the switch /3GB in your Boot.ini.

See the example:

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /noexecute=optin /fastdetect /3GB

This should address the extra memory in your PC.

Otherwise here is a link to Microsoft´s own explanation to the problem:

http://www.microsoft.com/whdc/system/platf...PAE/PAEmem.mspx

[Jito463]

According to that article, the /PAE switch does not work for 64-bit Windows.

Physical Address Extension. PAE is an Intel-provided memory address extension that enables support of up to 64 GB of physical memory for applications running on most 32-bit (IA-32) Intel Pentium Pro and later platforms. Support for PAE is provided under Windows 2000 and 32-bit versions of Windows XP and Windows Server 2003. 64-bit versions of Windows do not support PAE.