4GB RAM and Windows XP

Wai_Wai · October 30th, 2007, 01:00 AM

4GB RAM and Windows XP
I realise Windows XP (32-bit) supports up to 4GB RAM only.

However it says Windows XP needs to use some address space for your hardware, so only "4GB - address space reserved" will be usable in the operating system. That seems to mean some of your RAM are wasted due to the address space issues, aren't they? Thus

1. Since some of your RAM are occupied due to hardware address space issues, does it mean my RAM have been wasted (a waste of money to buy RAM that you can't use at all in any case)? If so, it seems to be wrong to think Windows XP can actually support up to 4GB RAM.

2. The above happens when I have 4 GB. Why doesn't it happen when I have 2 or 3 GB only? Doesn't our hardware still need to reserve memory space (or use some of my RAM)? Why am I able to use 100% of my RAM in the operating system when I have less RAM (but not when I have more)?

3. I wonder whether all these are display issues only. How much RAM being shown in the operating system doesn't change the fact that my hardware has to consume some of my RAM. Essentially they are using up the same amount of RAM in 2-3GB and 4GB cases. Buying 4GB doesn't make me waste more RAM than 2-3GB cases. Am I right?

ShyguyXPC · October 30th, 2007, 01:10 AM

From what I understand, could very well be wrong, but, the addressable memory is all of your memory in your system, your System RAM, plus Video Memory plus whatever else (not sure if CPU memory is included in this though.

so if your running say 3GB's & have a 512MB vid card, the total memory is sitting at 3.5GB's, where as if your running 4GB's, the total amount of addressable RAM is 4GB, so you'd have 3.5GB max of system RAM, as you'll need 512MB more space for your vid card... (so in effect only 512MB of your 4GB is wasted.)

or something along those lines, I know its not an exact/proper explanation of the situation, but does help to understand it some.

from what I've read on the problem in past, this is more or less how I understand it works?

RamonGTP · October 30th, 2007, 01:24 AM

Like Shyguy said, in a 32bit environment, you have 4GB of total addressable space. That includes video card, main memory as well as other components that require address space. So yes, if you're already reached the maximum addressable space, adding more ram will be wasted.

When I was running a 32bit OS and had 4GB of ram, I could only use 3.25GB of it. I also had a 512MB video card and the other 256MB was used by who knows what. When I upgraded to Vista, I went with the 64bit version for this very reason and I can now see/use all 4GB of my memory.

Wai_Wai · October 30th, 2007, 02:27 PM

Quote:

...so if your running say 3GB's & have a 512MB vid card, the total memory is sitting at 3.5GB's

But that 512MB RAM of video card is exclusive for video card. It can't be used by the system for other uses. Essentially we only have 3GB RAM usable in the operating system, haven't we?

RamonGTP · October 30th, 2007, 05:11 PM

Yes, but we are talking about total address space which includes the video ram.

ShyguyXPC · October 30th, 2007, 06:07 PM

Ramon's right, as I mentioned in first post.

Wai_Wai · October 31st, 2007, 01:13 AM

I see. Thanks for the clarification.

Mykex · November 2nd, 2007, 02:25 PM

Some motherboards will be quirky with the total as well, running an Intel P965 I would get a maximum 3.28gb even with the /PAE and /3.5GB switches in my .bat file (2.28 w/o switches).

Same video card (768mb GTS) and RAM in a P35 motherboard shows 3.5gb and will with the /PAE and /3.5GB switches installed or removed from the .bat file.

...both motherboards claim an 8GB max.

Dragonfam · May 9th, 2009, 04:53 PM

Quote:

Originally Posted by RamonGTP

Yes, but we are talking about total address space which includes the video ram.

How can you learn which components are taking address space? Is it possible to turn off components which you don't currently need or aren't using?

**RicheemxX** · May 11th, 2009, 02:38 AM

Kind of an old thread to dig up to ask and answer this question, but generally anything that has some sort of memory counts. Your video card, HDDs, the motherboards bios ect. But in those cases even if you could disable them you are talking about such small amounts (gpu aside) you wouldn't see any benefit from doing so.

The one single component that draws the most away from the total overall amount would be your video card and for obvious reasons you wouldn't want to disable that.

I've never actually benchmarked it, however at the point of 3.5 vs 4 gigs I doubt you'd really see that big a hit in terms of performance. Unless you are doing some serious mutitasking or running some seriously intesive apps, then you might see a small hit.