Microsoft OS Maximum Supported Ammount of RAM and Other OS related RAM issues - Overclock.net

ericeod · 12-28-07

Vista 32 and XP 32 support a maximum of 4Gb total memory. Vista 64 and XP 64 will run more then 4 GB of ram.
This total includes video card ram, i.e., you have a 512 MB so Windows will only recognize 3.5Gb of 4Gb installed ram.

Microsoft

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There is a work-around for the 4Gb memory issue. Microsoft 's work-around is known as Physical Address Extension, or PAE. This is an option if your hardware supports PAE (currently only Intel processors..see below), and only works with 32 bit operating systems:
Microsoft Windows 2000, Windows XP, and Windows Server 2003 products.

Microsoft

Quote:

To boot the system and utilize PAE memory, the /PAE switch must be added to the corresponding entry in the Boot.ini file. If a problem should arise, Safe Mode may be used, which causes the system to boot using the normal kernel (support for only 4 GB of RAM) even if the /PAE switch is part of the Boot.ini file.

What PAE is:

Quote:

PAE - Physical Address Extension - is an Intel-provided memory address extension that enables processors to expand the number of bits that can be used to address physical memory from 32 bits to 36 bits, through support in the host operating system for applications using the Address Windowing Extensions (AWE) API.

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Microsoft
For those running into the problem of BSOD when trying to run more then 3Gb of ram on Vista, you need to run the KB929777 hotfix from microsoft. This hotfix applies to Vista, both 32 bit and 64 bit, so download the corresponding update.

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Vista 32 Note:

Microsoft

Quote:

Various devices in a typical computer require memory-mapped access. This is known as memory-mapped I/O (MMIO). For the MMIO space to be available to 32-bit operating systems, the MMIO space must reside within the first 4 GB of address space.

For example, if you have a video card that has 256 MB of onboard memory, that memory must be mapped within the first 4 GB of address space. If 4 GB of system memory is already installed, part of that address space must be reserved by the graphics memory mapping. Graphics memory mapping overwrites a part of the system memory. These conditions reduce the total amount of system memory that is available to the operating system.

The reduction in available system memory depends on the devices that are installed in the computer. However, to avoid potential driver compatibility issues, the 32-bit versions of Windows Vista limit the total available memory to 3.12 GB. See the "More information" section for information about potential driver compatibility issues.

Note: When the physical RAM that is installed on a computer equals the address space that is supported by the chipset, the total system memory that is available to the operating system is always less than the physical RAM that is installed. For example, consider a computer that has an Intel 975X chipset that supports 8 GB of address space. If you install 8 GB of RAM, the system memory that is available to the operating system will be reduced by the PCI configuration requirements. In this scenario, PCI configuration requirements reduce the memory that is available to the operating system by an amount that is between approximately 200 MB and approximately 1 GB. The reduction depends on the configuration.

more updates to come

**ENTERPRISE** · 12-29-07

Thread Stickied by ENTERPRISE.

Please keep all information up to date when possible.

Thankyou.

decapitator · 12-29-07

what a cool thread i have been wondering about that for a few weeks now. running xp pro 32 and was thinking if buying two more gigs would be smart.

tangjuice81 · 01-01-08

I just purchased another 2gb of memory and I'm running Vista 32 so this helps alot. Thanks!

R3ap3R · 01-07-08

Thanks EricOD... I will link this sticky back in my guide.

EDIT: It is in my guide's thread, which is also a sticky now :-)

lowdanubnoxs · 01-18-08

I am a little confused. I just purchased 2gb more ram and am unable to boot into windows (luckily I have a linux partition). Since I can run Ubuntu with no problems I am sure my memory is fine. I now have 4gb ddr800 ballistix and I have reduced all timings and frequency to stock. PLEASE HELP! I want to play some games tonight, and gaming is the only reason I still deal with Microsoft.

ericeod · 01-21-08

Quote:

Originally Posted by lowdanubnoxs

I am a little confused. I just purchased 2gb more ram and am unable to boot into windows (luckily I have a linux partition). Since I can run Ubuntu with no problems I am sure my memory is fine. I now have 4gb ddr800 ballistix and I have reduced all timings and frequency to stock. PLEASE HELP! I want to play some games tonight, and gaming is the only reason I still deal with Microsoft.

Your ASUS motherboard should have a memory remapping feature that you need to enable in the bios. Try that and see if that works for you.

eXtr3m3 · 01-22-08

A friend of mine has 4x1Gb Corsair and he has just installed Windows Vista Ultimate 32bit and it says he has 3,5gb...how can he fix it?will SP1 fix it??

**ENTERPRISE** · 01-22-08

Quote:

Originally Posted by eXtr3m3

A friend of mine has 4x1Gb Corsair and he has just installed Windows Vista Ultimate 32bit and it says he has 3,5gb...how can he fix it?will SP1 fix it??

No. 32BIT Operating systems are limited to 3.5GB of RAM. the 32 bit addressing only allows the reading of 3.5GB.

To utilize 4GB + you need a 64bit OS.

charbs152 · 01-22-08

Quote:

Originally Posted by eXtr3m3

A friend of mine has 4x1Gb Corsair and he has just installed Windows Vista Ultimate 32bit and it says he has 3,5gb...how can he fix it?will SP1 fix it??

no he needs 64 bit vista

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Microsoft OS Maximum Supported Ammount of RAM and Other OS related RAM issues

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