Windows can't see 4GB of memory

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bountycode
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Windows can't see 4GB of memory

Post by bountycode » Thu Dec 23, 2004 1:40 pm

Ok I’ve googled this problem now for the last 2 days and couldn’t find an answer to this so I’m posting this here for some help. I bought a Abit AV8 motherboard and 4*1GB dims of memory. I’ve ran memtest86 on the memory and it checks out great. The Bios boot up screen shows me that I have 4GB of memory but when I get into Windows XP sp2 and go to My Computer -> Properties it shows I only have 3.00 GB of Ram.

system properties

Also the task manager shows I only have 3.1452 GB of physical memory. And btw physical address extension seems to be on according to system properties. So what gives? Any ideas why windows xp can’t see 4GB of memory?

Task Manager[/url]

Lax
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Post by Lax » Thu Dec 23, 2004 2:04 pm

After doing some research, it may not matter that it only shows 3GB
Any 32 Bit operating system such as Windows (NT4.0, 2000, XP) or Linux can manage a maximal amount of 4 Giga Bytes (GB) of memory. On Windows however the upper 2 GB are reserved for system DLLs and drivers. Therefore, a single application can at maximum use 2 GB of memory. Note that this is independent of the actual physical memory, i.e. it does not matter whether the system has 1, 2, 3 or 4 GB of memory installed. In the first 2 GB the software itself (executable and all its DLLs) and all the data has to fit. This makes clear that it is impossible for a windows program to load 2 GB of data at a time.
To overcome this Microsoft has provided a boot option for Windows XP that shifts the 2 GB limit to 3 GB.
http://www.amiravis.com/3GBswitch-instruction.html

Exploding Kitchen
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Post by Exploding Kitchen » Fri Dec 24, 2004 4:21 am

Feel free to ship the excess RAM to me. Thanks!

:P

bountycode
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Post by bountycode » Wed Jan 05, 2005 4:00 pm

Seems that SP2 breaks windows ability to see 4GB of ram. Lax is there any way to get around this "fix"? disable PAE mode? As far as I understand it you should only need PAE mode if you have more then 4GB of ram. Servers at work here have 8GB of ram and they need the /PAE option added to the boot.ini file. But my boot.ini file does not have the /PAE option in it yet it's running in PAE mode somehow.

here is the link "explaining" kinda why it's not seeing the memory but it does not say how to fix this problem.

http://support.microsoft.com/default.as ... -us;888137
CAUSE
This issue occurs because of a design change in Windows XP SP2. The changes were made to PAE mode behavior to improve driver compatibility.

Lax
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Post by Lax » Wed Jan 05, 2005 4:44 pm

I really dont know.. I'm no Microsoft expert. The only thing I found that would help is the /3GB switch, past that you really have to talk to Microsoft. I can try to find out for you from my MS contacts, but they work in departments that are unrelated to your issue, so I cant promise anything there.

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