2x2gb dimms only registering as 2.98gb?

[stutters]

i just installed 2x2gb dimms into my macbook pro, booted into xp, and the system properties tab only shows 2.98gb. is that normal/right?

[dwEEziL]

For 32-bit Windows, yes. Typically, you'll see between 3GB and 3.5GB (depending on what other memory you might have already recognized such as your vid card).

[stutters]

all windows 32bit, including vista?

[anonymo]

all windows 32bit, including vista?

Yes. Only 64bit recognizes more than 3~3.5gb

 

What are you new?

[Sgt. Slaughterâ„¢-TopBrass]

Vista 32bit will recognize 4GB, as for XP I thought service pack 3 was suppose to fix that.

[Playaa]

Also your Macbook Pro may not recognize more than 3gb on it's own depending on what version it was.

Mine which is the one right before the LED backlit screens has 2x2gb installed but only recognizes 3 due to the bus...or taxi or something.

[dwEEziL]

He's getting engaged. He has to hand over half his brain and all of his genitals. Cut him some slack.

[shoot]

* 32-bit versions of Windows Vista Home Basic, Home Premium, Business, Enterprise, and Ultimate: 4GB

* 32-bit Windows Vista Starter: 1GB

* 64-bit versions of Windows Vista Home Basic: 8GB

* 64-bit versions of Windows Vista Home Premium: 16GB

* 64-bit versions of Windows Vista Business, Enterprise, and Ultimate: 128GB

 

Below explains a bit about "why" less than 4GB, even though, technically, your computer IS using the 4GB.

 

This paper from HP helps explain it–the platform can theoretically support the full 4GB, but your hardware is going to allocate some of the address space (not the physical RAM) to the PCI bus, the video adapter memory address space, and other resources. 32-bit OSs need to use part of the full 4GB address space to address these resources, subtracting from the maximum memory you have available to the OS and applications:

 

The PCI memory addresses starting down from 4 GB are used for things like the BIOS, IO cards, networking, PCI hubs, bus bridges, PCI-Express, and video/graphics cards. The BIOS takes up about 512 KB starting from the very top address. Then each of the other items mentioned are allocated address ranges below the BIOS range. The largest block of addresses is allocated for today’s high performance graphics cards which need addresses for at least the amount of memory on the graphics card. The net result is that a high performance x86-based computer may allocate 512 MB to more than 1 GB for the PCI memory address range before any RAM (physical user memory) addresses are allocated.

 

So, if your video adapter has 512MB of RAM (like mine does), your maximum memory is going to at most be 3.5GB, because Vista has to use 512MB of that address space to address your video memory. It’ll actually be lower than the 3.5GB because there are other hardware resources that need address space, too. So, it never hurts to fill your computer with 4GB of RAM–you’ll definitely get the max, but you won’t be able to address it all. You probably won’t be able to address much more than 3GB, and you might not be able to address more than 2GB.

The paper also mentions something interesting about 64-bit computers. Basically, depending on the hardware, you might be limited to 4GB of RAM even if you install 64-bit Windows Vista:

 

Windows XP Professional x64 Edition uses 64-bit addressing enabling virtually the entire amount of installed RAM to be made available on computers that have large address infrastructures (where the entire system has more than 4 GB addressing capabilities via the processor, chipset, physical memory capacity, etc). The HP xw4300, xw6200, xw8200 and xw9300 Workstations have the required infrastructures and even the PCI memory address range is recovered by re-mapping it above the top of physical memory.

 

 

 

Link to this article

[shoot]

Also your Macbook Pro may not recognize more than 3gb on it's own depending on what version it was.

Mine which is the one right before the LED backlit screens has 2x2gb installed but only recognizes 3 due to the bus...or taxi or something.

 

I think he's got the newer one that will use the 4gb. He just got it, didn't he?

Edited October 3, 2008 by shoot

[stutters]

yeah, 2.4 c2d takes the full 4gb. if given a choice, i'd like to stay with xp, i just didn't have the time to do the sp3 install right now. but then again, half the people are saying it won't work on 32bit os (period), the other half are saying it will work on sp3 xp 32bit. yeah, and because 3/4 of my brain is somewhere else right now, i didn't even try to read beyond the first sentence of whatever shoot posted.

 

between all the versions of windows, you folks sure make it a lot harder than it needs to be.

[dwEEziL]

Hey, we didn't choose for 42 different versions of Windows...we just deal with it.

[bushwack]

My XP reports 3.25 out of 4gb but I heard that drivers and some other stuff can reside in the other unreported chunk of the memory, giving more room then you actually think you have.

[anonymo]

yeah, 2.4 c2d takes the full 4gb. if given a choice, i'd like to stay with xp, i just didn't have the time to do the sp3 install right now. but then again, half the people are saying it won't work on 32bit os (period), the other half are saying it will work on sp3 xp 32bit. yeah, and because 3/4 of my brain is somewhere else right now, i didn't even try to read beyond the first sentence of whatever shoot posted.

 

between all the versions of windows, you folks sure make it a lot harder than it needs to be.

 

Shoot's post smallerized: Windows XP 32bit may not display all 4gb but it uses it, trust us. Even pre-SP3 it used it. Only 64bit versions however display the full installed ram properly. Please note the difference between display and use.

[Preacher]

It may not say you have 4gb but it still uses all 4gb. It may display as cache memory but all 4gb of RAM are utilized.