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The 32-bit, 4 GB problem

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January 19, 2010 5:11:01 AM

Default The 32-bit, 4 GB problem


Okay, just upgraded my RAM from one 2GB DIMM to two 2GB DIMMs. I was well aware of the 32-bit problem, but thought that 3.5GB of that 4GB should show up-- but only 3GB does.



I know that there is no way to see the full 4GB in 32-bit Windows-- but is there a way I can bring it up to 3.5? Any way to limit PCI memory range in the BIOS or something? I have a 256MB PCIE video card, but am not a gamer and really don't need any more memory than is necessary as a frame buffer for both my monitors at full resolution.



http://webpages.charter.net/garrison6328/cpuz/cpuz.htm



my motherboard:



http://www.biostar.com.tw/app/en-u [...] p?S_ID=315



my video card:



http://www.tigerdirect.com/applica [...] 11&NoMapp=

More about : bit problem

a b V Motherboard
January 19, 2010 10:58:57 AM

The total amount of addressable space that Windows can allocate is 4GB, and thats counting space reserved for HW components.

For most people, the GPU/Motherboard eats up 1GB of that free space, leaving us with 3GB avaliable.
January 19, 2010 2:10:48 PM

check agp aperture in bios, see what is reserved, and that PAE is enabled in os and bios...

what is reported is not the limit, if it is there, it is used.

I am maxxed too, 4 gb, 512 card, firnware hub, and further...ECC disabled on two of the four dimms, leaving even more space....never to get a number out loud.... :pt1cable: 

thread it all as much as possible, and go with it.
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January 20, 2010 4:04:45 AM

that is because you use OS 32-bit version. i have the same problem as u, once. i upgraded my RAM from 2GB to two 2GB as you did, but it only read 3.25GB in my system. and when i installed windows 7 64-bit, the system shown full of my ram, 4GB.

you could use windows XP 64-bit instead of windows 7 64-bit if you like.
January 20, 2010 6:13:42 AM

u can try to edit the maximum value in the bios because that's what the problem at first hand. my pc has a maximum of 3.25 GB RAM.

also there are more threads about this and most motherboards only support a maximum of 3 GB or 3.25 GB usage.

read the link below ("it says if u want to use all 4GB u will need to buy 64x"):
http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/A...
a b V Motherboard
January 20, 2010 6:19:18 AM

as gamerk said, the 4gb limit includes VRAM on your video card. so this is normal.

January 20, 2010 10:31:26 AM

The maximum is 4GB. The GPU/Motherboard uses 1GB.
a b V Motherboard
January 20, 2010 11:44:00 AM

Its not a Windows problem, its not a motherboard problem, its not a Bios problem. Its a counting problem.

The CPU, when operating in 32 bit mode, can only count a string of 0's and 1's that is up to 32 numbers long (IE: A string of 32 consecutive 0/1 values). The maximum number of cominations you can get from this string can be expressed as 2^32 = 4.2 Billion = 4GB. The best you can do on a 32 bit OS is make the extra RAM visable, although it won't actually be used.

Since Windows allocates space for HW first, any devices (usually the GPU) get assigned first, taking away from the maximum number of memory locations that can be accessed.

PAE is basically a hack that can be used to allow for the full 4GB of system RAM to be usable on a 32-bit system, although it carries the risk of incompatable SW/drivers. Its not a recommended fix. And even then, because Windows automatically reserves 2GB of the avaliable RAM for Kernal use, each application is still limited to only 2GB of RAM.
January 20, 2010 1:36:20 PM

gamerk316 said:
PAE is basically a hack that can be used to allow for the full 4GB of system RAM to be usable on a 32-bit system, although it carries the risk of incompatable SW/drivers. Its not a recommended fix. And even then, because Windows automatically reserves 2GB of the avaliable RAM for Kernal use, each application is still limited to only 2GB of RAM.


It makes no sense to talk about the virtual address space layout when talking about the problem with the physcial address space. They are not related.

And you are the guy that wants to teach other people about this stuff?
a b V Motherboard
January 20, 2010 4:00:25 PM

^^ They ARE related. As I already explained once. Or are Page Tables to difficult for you to understand?

Physical Address Space: The amount of space that can be accessed at any one point in time. (4GB in a 32 bit system)

Virtual Address Space: The total amount of space for all programs in use; Each virtual address is mapped to a physical address when the page is loaded.

PAE Extends the Physical Address Space to 64GB (via 36-bit mode), but the Virtual Address Space limit of 2GB per application [due to kernal overhead] remains; hence why PAE is not a permenant fix. It does allow for the extra RAM up to the first 4GB to be fully accessed in all cases, however.

And again, since you didn't read it the first time: The IA32 architecture documentation, stright from Intel:

http://www.intel.com/support/motherboards/desktop/d845e...

Now Mikrev, either make a point [with actual evidence], or stop trolling.
January 20, 2010 4:49:32 PM

Quote:
because Windows automatically reserves 2GB of the avaliable RAM for Kernal use


RAM?

I have seen you write this several times, where you clearly misunderstand the difference between the virtual and physical address space.

Related? How can you say that 2GB user space and 2GB kernel space is related to how the physical memory space is populated? It is not. And then you talk about page tables... they too are not related to the issue.

PAE makes it possible to use a larger physical address space. So what? Your crying out about the limited 4GB virtual address spaces belongs in threads about 32bit vs 64bit OSes.

Can you guess how you address physical memory in a 64bit OS? What is the structure of the PTE? Can you tell me the difference in addressing memory in 32bit OSes vs 64bit OSes when you execute 32bit applications?
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