XP only showing 3gig of the 4gig memory

Random

Motherboard: Asus A8N-SLI Deluxe
OS: Windows XP Pro
Memory: 4x 1GB Corsair TwinX Matched Memory Pair

The post screen shows 4GB memory.

CPUID shows 4GB


Windows seems to only show 3GB.



Does this mean XP is only picking up 3gig?

Thanks

encryptix

do you have a sound card or graphics card?

Random

I use the onboard sound.
I have a separate graphics card and no onboard graphics.

tman

Installing SP3 should make it recognize some more of it, but it still won't utilize it properly...

Random

So it's a XP limitation that it only supports >3GB with SP3?

Outkast_IRE

Dont 32bit windows only recognise 3gb. As far as i know you need 64 bit windows vista or xp for it to recognise more. This is one of the upsides of a 64bit os i have 8gb

Random

My OS is the 32bit one.

tman

With SP3 it will report that you have 4GB of ram, but still won't actually use it. You would need to switch to the 64 bit versions of XP or Vista to make use of it
It's no real worry anyway, 4GB is serious overkill for XP!

Jonathan

It is a limitation of a 32bit os.


2^32 less memory assigned to hardware etc leaves you with about 3.25gb.

Random

The reason I have 4GB is because I sent away 4x 512MB to Corsair faulty and they sent me back 4x 1GB which I've just put in. Very nice of them really

Is it a bad thing to leave the 4GB in? Am I better off giving away 2GB?

tman

Score!
No harm leaving it in really... I know I would in your situation

Random

My OS isn't using it. When I upgrade chances are DDR isn't much use any more.

Right ?

Jonathan

Random wrote: »

My OS isn't using it. When I upgrade chances are DDR isn't much use any more.

Right ?

Right. Give it to me instead. :pac:

encryptix

is the limitation not 4gb with a 32 bit os? so with a graphics card (Say 512mb) wouldnt that leave ~ 3.5 GB
??

if you wanted to use the extra 1 gb memory you have you could get a 64bit os....but with xp 3 GB is more than enought

edit: just seen the 64 bit os was already said

samhail

errr... isnt virtual ram and physical ram taken into account together in the ram available. try adjusting your virtual ram and see what happens

Outkast_IRE

samhail wrote: »

errr... isnt virtual ram and physical ram taken into account together in the ram available. try adjusting your virtual ram and see what happens

No it isnt the program hes using cpu-z only takes into account physical ram and adjusting the virtual would make no difference

watty

It's a deliberate XP limitation. NT4.0 enterprise can do 4G.

However I upgraded my 512M to 768M on XP and usage has never exceed about 390M.

samhail

i might actually be thinking about vista too. my bad.

harney

How much memory is your bios showing, the board may not be able to handle 4GB. I have the same issue with my laptop. The bios only shows 3.3GB of the 4.

If you bios shows 4GB then you can look at modifying the boot.ini file and adding the /PAE extension.

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx

Capt'n Midnight

jmccrohan wrote: »

It is a limitation of a 32bit os.

2^32 less memory assigned to hardware etc leaves you with about 3.25gb.

No it's not :rolleyes:

http://support.microsoft.com/kb/268363

Windows 2000 Advanced Server and Windows 2000 Datacenter Server support memory in excess of 4 gigabytes (GB) of random access memory (RAM) by way of the Intel Physical Addressing Extension (PAE) specification. Windows 2000 Advanced Server is limited to 8 GB, and Windows 2000 Datacenter Server is limited to 32 GB. You can enable PAE in the Boot.ini file.

the 4GB limit is like the old 1MB limit in Dos you can get beyond it with tricks involving memory address swapping,

The problem is that microsoft don't have any incentive to sort it out. The hardware industry is moving to 64bit which doesn't have the same limit. And the limits have a lot to do with marketing too. Windows 2000 PRO has mostly the same files as this

http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx
Windows 2000 Datacenter Server = 32 processors and 32 GB RAM (support for 64 GB was not offered because of a lack of systems for testing)

leninbenjamin

Capt'n Midnight wrote: »

The problem is that microsoft don't have any incentive to sort it out.

isn't really the fundamental issue with 32bit OS is that they can only set aside at most 2GB RAM for any single application? so even if they did expand on it there'd be no point because very few people would be using more than one single demanding application at a time...

Capt'n Midnight

leninbenjamin wrote: »

isn't really the fundamental issue with 32bit OS is that they can only set aside at most 2GB RAM for any single application? so even if they did expand on it there'd be no point because very few people would be using more than one single demanding application at a time...

you can get 3GB per app in some versions of windows server
http://technet.microsoft.com/en-us/library/bb124810.aspx

think of it as 2GB per thread

or you could have a RAM drive , it's a very old low tech way of giving more memory to apps or allowing them to swap data

http://support.microsoft.com/kb/72099 Windows 3.0 could only see 16MB of ram so you if you have 64MB of RAM you'd setup a 48MB swap file in a ram drive

watty

However unless you are running a Global Climate Change Model, terribly badly written software or Crysis there is no reason why an application even needs 512M.

It's nothing really to do with 32bits vs 64bits but how motherboards, cpus and OS is designed.

A lot of motherboards are very strict on the amount of RAM they reserve for hardware addressing. Chances are that not all of the reserved 1GB is used.

About PAE, Microsoft removed support for 36-bit addressing in XP SP2 claiming stability concerns. This means the OS is limited to ~3GB max, even if you add the /PAE switch to boot.ini. PAE is now only used for the NX/XD bit.

Random

I'm gonna just sell 2x 1GB chips and keep the other 2 I reckon.

Cool Mo D

Ok, the real reason that you can only access 3GB has been alluded to here - but here is a slightly fuller explanation.

Originally, all 32bit OSes had a theoretical memory limit of 4GB of physical address space, back in the days when this was a huge amount. Using physical address space is the easiest and fastest way for a device to communicate with the CPU (the other way is called I/O ports). Many devices will will map themselves to physical address space - RAM most importantly, but also, video cards, and any device that needs quick access to the CPU.

In time, computers started running close to the 4GB limit that a 32bit OS can give, so newer motherboards started using tricks to map extra RAM (but not devices), so a 32bit OS could have way more than 4GB RAM.

Windows, no less than any others, incorporated these improvements. However, this caused big problems with lazily written device drivers from companies like nvidia and amd, that assumed a max 4GB of RAM, and tended to crap themselves if they saw more.
So, in original XP, it was possible to install and use 4GB of RAM, if you had a suitable motherboard. In XP service pack 1, this was "fixed" to max 4GB - whatever memory was used by other devices, to prevent buggy drivers crashing PCs. It's still possible to use more than 4GB of RAM on 32bit server OSes from microsoft - they assume people using these will be able to locate suitably compatible graphics hardware and drivers.

If you want to use 4GB, you'll have to install Vista 64GB, although, technically, pre service pack 1 XP might be an option, no-one in their right mind would recommend that.

So, to summarise, 32bit OSes can use more then 4GB RAM, but it need suitable hardware and software, and no consumer 32bit microsoft OS counts as suitable software.

Here's a screen grab I took about a year and a half ago when I was bored and built a test rig to prove what I had studied:



This was with the /PAE switch. Removing it dropped the reported RAM back to 3.25GB.

XP never shows the total installed RAM like Vista SP1 does, not even in SP3. My laptop has 4GB and only shows 3GB on SP3.

PaddyTheNth

Cool Mo D wrote: »

If you want to use 4GB, you'll have to install any 64-bit flavour of Windows, although, technically, pre service pack 1 XP might be an option, no-one in their right mind would recommend that.

Tidied that up for you...never know when someone will take you literally.

Though it obviously can be hacked if you know what you're doing, as Karsini's screenie shows.

PaddyTheNth

PaddyTheNth wrote: »

Though it obviously can be hacked if you know what you're doing, as Karsini's screenie shows.

Nah it's not worth the effort. Getting a virus as soon as you connect to the net isn't fun!

PaddyTheNth

Karsini wrote: »

Nah it's not worth the effort. Getting a virus as soon as you connect to the net isn't fun!

Really? lol

A couple lads I know messed about with PAE, they said it took a huge amount of effort to get the system stable.

astrofool

The hacks to get 32 bit windows to recognise >4GB also seriously increased memory access time. It was only really (effectively) used to keep large databases in memory, where the access time to the hard disk was much much more.