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Windows 7 useable ram less than installed ram

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andy2dapond

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Nov 12, 2009
Location
Massachusettes
hey guys i just recently upgraded to windows 7 and i was inspecting my computers info and came across that i physically have 4 gigs of ram installed, but only 3 gb of ram is use able? can anyone tell me if this is correct or some type of problem and how i could use all 4 gigs of my ram? thanks!
 

johnz

Member
Joined
May 30, 2004
If it's Win7-32bit you'll have to get the 64bit version. If you have 64bit installed, look in your BIOS options for memory remapping, and turn it on.

Edit:
I need to look at the information provided :^D

You need the 64bit version. Daddyjaxx gave you the easy way. If you have oem it could be a bit more problematic.
 
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freeagent

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Sep 15, 2004
Location
Winnipeg!
hey guys i just recently upgraded to windows 7 and i was inspecting my computers info and came across that i physically have 4 gigs of ram installed, but only 3 gb of ram is use able? can anyone tell me if this is correct or some type of problem and how i could use all 4 gigs of my ram? thanks!

Yes its normal, 32bit windows can see all of your ram, but can only address 4gb, that includes your video memory.

If you have 4gb of ram installed, and a gpu with 1gb, windows can address all of your video memory, and 3gb of system ram. If you have a soundcard with say 64mb of ram, that would also be deducted from the total amount you have.
 

Bluefalcon13

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Jan 1, 2008
Location
Colorado Springs, CO
Yes its normal, 32bit windows can see all of your ram, but can only address 4gb, that includes your video memory.

If you have 4gb of ram installed, and a gpu with 1gb, windows can address all of your video memory, and 3gb of system ram. If you have a soundcard with say 64mb of ram, that would also be deducted from the total amount you have.

Actually, there is more to it than that...

32bit supports 4gig of ram TOTAL memory addressing. HDD cache, CPU cache, NVROM on MB, etc etc. will all eat up addressing resources and lower your total amount of 'availible memory'.

Example, my setup in sig with 4 gig installed shows only ~3.5 gig in XP 32bit. When I install an additional 2 gig (for 6 total), XP 32bit only shows 3gig of RAM availible. Note, I have 320MB video card, as well as 3 80G HDDs.
 

hansen

Member
Joined
Oct 26, 2007
32bit supports 4gig of ram TOTAL memory addressing. HDD cache, CPU cache, NVROM on MB, etc etc. will all eat up addressing resources and lower your total amount of 'availible memory'.

Not everything is mapped into the addressable memory space of the CPU. Things that you cannot address wont be mapped. Like cache on your harddrive... that is internal to your harddrive. The Lx cache on the CPU is not a part of it either. That is also internal stuff.
 

hokiealumnus

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Joined
Oct 14, 2007
Example, my setup in sig with 4 gig installed shows only ~3.5 gig in XP 32bit. When I install an additional 2 gig (for 6 total), XP 32bit only shows 3gig of RAM availible. Note, I have 320MB video card, as well as 3 80G HDDs.
I'm somewhat confused. With 32-bit, of course it won't increase your RAM amount to add the additional 2G because it's out of address space...but why would it decrease the RAM showing by .5G?
 

nd4spdbh2

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Nov 15, 2005
Location
Camarillo, CA!
This is why it's close to criminal that M$ are even make a 32 bit version :D

umm no, people still use 32bit components.... ie Netbooks, which are like the hotest thing out right now.

I'm somewhat confused. With 32-bit, of course it won't increase your RAM amount to add the additional 2G because it's out of address space...but why would it decrease the RAM showing by .5G?

its 4gb max total memory of the system in a 32bit os. so when you have a gfx card with 512mb, a hd with 32mb cache, a 4mb cpu cache yadi yada your down around 3.4gb of addressable memory left which is what the 32 bit os sees.
 

hokiealumnus

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Oct 14, 2007
its 4gb max total memory of the system in a 32bit os. so when you have a gfx card with 512mb, a hd with 32mb cache, a 4mb cpu cache yadi yada your down around 3.4gb of addressable memory left which is what the 32 bit os sees.
No, I fully understand that. In his post, he said his system shows 3.5G of memory with 4G installed. When he installs an additional 2G for six total, it shows 3G. My question was asking where the remaining .5G disappeared to simply by installing the unusable RAM. Probably a typo, but in case it wasn't, I'm curious.
 

Bluefalcon13

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Not everything is mapped into the addressable memory space of the CPU. Things that you cannot address wont be mapped. Like cache on your harddrive... that is internal to your harddrive. The Lx cache on the CPU is not a part of it either. That is also internal stuff.

Guess I went a little too far in including EVERY thing, but the point remains, expansion cards addressable memory also eat addresses, as well as your mobo. I was under the impression that the L2 did get mapped by the OS as it has usable addresses... but I could be wrong.

I'm somewhat confused. With 32-bit, of course it won't increase your RAM amount to add the additional 2G because it's out of address space...but why would it decrease the RAM showing by .5G?

I've wondered that myself, and my guess is that due to PAE (Physical Address Extension) that windows XP actually maps the extra memory, but it is unusable by programs in a common sense. Either that or it used additional addressing space to utilize all 4 DIMMs rather than just the 2x2gb DIMMs... but I never really looked that deeply into it. If I still had a working 32bit XP partition, I'd take some screenies to post here, but Sunday the XP install finally kicked the bucket via BSOD every 3-5 mins including the bootup time. So rather than reinstall XP and migrate to 7 later, I backed everything up on the drives from Win7RC1(separte boot drive) and installed the Win7 Retail(x64).
 

hokiealumnus

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Oct 14, 2007
No screenies needed, I believe you. :) That is a very curious phenomenon. Your explanations sound as plausible as any.
 

Neuromancer

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Oct 11, 2005
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Tau'ri
No, I fully understand that. In his post, he said his system shows 3.5G of memory with 4G installed. When he installs an additional 2G for six total, it shows 3G. My question was asking where the remaining .5G disappeared to simply by installing the unusable RAM. Probably a typo, but in case it wasn't, I'm curious.

I would guess it was a board limitation. IE it is now only seeing 1 2GB+1GB sticks rather than 2 of each

Or it is only seing half of each dimm.

Because it passes the 4GB limitation of the board itself. (without changing BIOS)

just a guess :)
 

Bluefalcon13

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Colorado Springs, CO
No screenies needed, I believe you. :) That is a very curious phenomenon. Your explanations sound as plausible as any.

I was would post em just so I feel more sane... not that that would fix my brain :p

It is important to note, even if your system only shows X RAM but really has Y RAM installed that it CAN use some of that that is left over, via PAE (Physical Address Extension). If I recall correctly, the additional RAM can be used by low-level resources (IE lower than OS) for things (I think a valid example of this would be Firewire, which has the access to utilize system some hardware directly, without interfacing with an OS- there were some security vunerabilites with Firewire connections between a Windows computer and an attacker which allowed the attacker to run a program to modify the Windows machine's login passwords and such).
 

Bluefalcon13

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Jan 1, 2008
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Colorado Springs, CO
I would guess it was a board limitation. IE it is now only seeing 1 2GB+1GB sticks rather than 2 of each

Or it is only seing half of each dimm.

Because it passes the 4GB limitation of the board itself. (without changing BIOS)

just a guess :)

couldn't be, cause without a BIOs/HW change, and swaping between RC1 x64 and XP-32bit would yeild the 6gig vs. 3gig, then if I pulled the 2gig kit (2x1gig) and rebooted into xp it would register ~3.5gig RAM


edit: I guess it may have been how Windows mapped the RAM without exceeding the avaible addresses though... didnt think about that... could have used one DIMM of each
 
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Neuromancer

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Tau'ri
LOL which is why I said It was a guess ;) Must be something in windows then, in order to use all 4 DIMMs it has to halve the amount of data it can receive from each dimm (same thing I said but windows based instead of HW based :) )
 

petteyg359

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Jul 31, 2004
I've wondered that myself, and my guess is that due to PAE (Physical Address Extension) that windows XP actually maps the extra memory, but it is unusable by programs in a common sense. Either that or it used additional addressing space to utilize all 4 DIMMs rather than just the 2x2gb DIMMs... but I never really looked that deeply into it.

The PAE support in most 32-bit Windows is a small subset, to allow DEP to function. It doesn't actually allow utilization of additional memory. I don't know the specifics of how DEP works or why it requires PAE.
 

Bluefalcon13

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Colorado Springs, CO
The PAE support in most 32-bit Windows is a small subset, to allow DEP to function. It doesn't actually allow utilization of additional memory. I don't know the specifics of how DEP works or why it requires PAE.

I do not think that is 100% accurate... while 32-bit Windows (non-server editions) only allows for 4gigs of memory (even with PAE), prior to my upgrade from 2 gig to 4GB/6GB RAM, Physical Address Extension was not listed after right-clicking computer and going to properties (system info listed on the window that pops up), but once I exceeded that limit of Physical addresses by installing additional ram, it shot me over the limit, hence auto-engadging PAE as per the MS info papers I read.

Link: http://msdn.microsoft.com/en-us/library/aa366796(VS.85).aspx

According to that, DEP needs to be enabled to automatically use PAE on XP/Vista/7 32-bit OSes

Quote from link:

Windows automatically enables PAE if DEP is enabled on a computer that supports hardware-enabled DEP, or if the computer is configured for hot-add memory devices in memory ranges beyond 4 GB. If the computer does not support hardware-enabled DEP or is not configured for hot-add memory devices in memory ranges beyond 4 GB, PAE must be explicitly enabled.
 
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