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#1 2009-04-28 17:07:09

göteborg-johan
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Registered: 2009-02-27
Posts: 36

[SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

Hello, I just upgraded my RAM-memory from 2gb to 4gb on my 32bit system, but somehow free -m, htop and top only says that i have about 2.5gb, surely something must be wrong here?

I tried to google it and asked around a little bit and even tho 4gb is max on 32bits systems, i should be getting a lot more than 2.5gb. I've checked in bios and it seems like all the 4gb is being recognized there atleast.

Anyone have any toughts on what could be causing this? It kinda sucks doubling your RAM-memory but only getting about 500mb out of it. hmm

Last edited by göteborg-johan (2009-04-29 20:43:42)

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#2 2009-04-28 17:21:05

brisbin33
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From: boston, ma
Registered: 2008-07-24
Posts: 1,796
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Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

you're probably at the ~3.2 GB limit that's imposed by being a 32 bit OS; then subtracting kernel and video memory (all depending on your system setup) could get you to that 2.5 number you're seeing.

that's just a guess though, someone else should chime in if more knowledgeable

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#3 2009-04-28 17:54:59

vi3dr0
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From: Poland
Registered: 2009-03-22
Posts: 208

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

I agree with brisbin33. You could recompile kernel with added PAE support to use up to 4 GB (i suppose around 3.5 in your case).


Thinkpad T61p : T7700 | 4GB RAM | nVidia FX 570M | Intel 4965
Arch64 @ Openbox

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#4 2009-04-28 17:57:33

göteborg-johan
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Registered: 2009-02-27
Posts: 36

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

vi3dr0 wrote:

I agree with brisbin33. You could recompile kernel with added PAE support to use up to 4 GB (i suppose around 3.5 in your case).

Sounds like quite a project, but I'll look into it, thanks. I read somewhere that support for large memory was built in by default, but i guess that is not the case then?

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#5 2009-04-28 19:00:08

broch
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From: L.A. California
Registered: 2006-11-13
Posts: 975

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

I would not bother (with kernel re-compiling): 32-bit arch kernel supports up to 4GB
There are other things to check. But make sure that your BIOS really sees 4GB of RAM

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#6 2009-04-28 20:38:39

göteborg-johan
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Registered: 2009-02-27
Posts: 36

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

Just checked, 100% sure bios sees all the 4 gb of RAM. What would the other things be to check?

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#7 2009-04-28 22:07:50

broch
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From: L.A. California
Registered: 2006-11-13
Posts: 975

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

My mistake
it looks like Arch kernel (or rather vanilla kernel) does not enable PAE along HIGHMEM4GB. You need to set HIGHMEM64G to enable PAE. In turn this will allow kernel to use all memory (4GB).

I am not sure if this is bug in vanilla kernel (most likely) or special feature.

This requires kernel recompilation with setting HIGHMEM64GB

Now how much you will actually see depends on GART, BIOS options for memory remapping and so on. Really depends on your mobo.

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#8 2009-04-29 14:31:51

göteborg-johan
Member
Registered: 2009-02-27
Posts: 36

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

I guess it would be easier to just install 64-bits then, instead of modifying the config every time there is a kernel update. Is it so simple that you just keep the home partition the way it is, and then just reinstall all packages and it should work? Xorg settings HAL policies would probably be a good idea to backup too but that's basically it, right?

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#9 2009-04-29 16:26:44

scio
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From: Buffalo, NY
Registered: 2008-08-05
Posts: 366

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

Be sure your hardware supports a 64bit OS first.

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#10 2009-04-29 16:31:16

göteborg-johan
Member
Registered: 2009-02-27
Posts: 36

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

scio wrote:

Be sure your hardware supports a 64bit OS first.

It's a Core2Duo E7300, it should be no problem.

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#11 2009-04-29 16:50:37

brisbin33
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From: boston, ma
Registered: 2008-07-24
Posts: 1,796
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Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

i also posted this when i went 32->64; posts 1 and 29 may be useful

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#12 2009-04-29 20:06:42

göteborg-johan
Member
Registered: 2009-02-27
Posts: 36

Re: [SOLVED, KIND OF]Upgrade of RAM on 32bit not showing correctly?

brisbin33 wrote:

i also posted this when i went 32->64; posts 1 and 29 may be useful

Thanks smile

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