RAM expansion / upgrade for 32-bit XP system

  malynx 15:07 28 Jan 2013

Hi. I apologise as I know this is an oft-raised topic, but the more I read the more confused I get.

I'm wanting to add extra RAM to the existing 2 x 1GB (PC3200) but am unsure as to how much is actually worthwhile adding due to 32-bit Operating System limitations. My budget is very tight so I really don't want to be adding 2 x 1GB if it brings no advantage over adding 2 x 512MB.

My system specs are: OS: Windows XP (Professional SP3) 32-bit;
MOBO: ASUS A8N SLi Deluxe (with four memory slots);
CPU: AMD 64 Athlon X2 Dual Core 4400+ (2.2 GHz, 1MB L2 cache);
RAM installed: 2 x 1GB PC3200 DDR400;
Graphics Card: 512MB ATI Radeon HD 5670.

I understand that I can install a maximum of 4 x 1GB RAM sticks, and that for best results I should use pairs. I know that 32-bit XP won't recognise a full 4MB of RAM (but I'm not sure why, nor how much it will recognise. Does "not recognise" mean there is no point in it being there?). However sometimes I've read that the maximum RAM is 3.5GB and sometimes 3.1GB. The latter figure makes me think that having more than 3GB of RAM isn't cost effective. Just to confuse me further, I've read that any memory on a graphics card is part of the 4 GB maximum (or is it 3.5 GB maximum?)of the operating system. As I have a 512GB graphics card, would I be better off adding just 2 x 512MB RAM, or would 1 x 1GB stick be just as good (as I was told in a computer shop at the weekend)?

The System Information application informs me: "Total Physical Memory 2,048.00MB; Available Physical Memory 1.19GB." Is that it that the full 2GB isn't available?

  alanrwood 15:31 28 Jan 2013

If you want to be able to use the maximum possible memory for your operating system and motherboard add 2 x 1GB sticks. The maximum the 32 bit WinXP can access is around 3.4GB which was arbitrarily set by Microsoft. It's a question of how much you want the extra 0.4GB againmst the additional cost of a 1GB stick which will only be half used.

  alanrwood 15:33 28 Jan 2013

PS You might find that this old type of RAM is quite expensive

  malynx 22:51 28 Jan 2013

Thanks Alanrwood

yes, it is quite expensive, and twice as much here in Australia than in the UK, which is why I don't want to buy more than will be of use.

So, the 512 MB of graphics card memory isn't a factor?

  Number six 23:35 28 Jan 2013


I always found that XP would chug along quite happily with 2GB RAM. Adding any more may only show very marginal improvements in performance. Considering the high cost of compatible RAM these days, are you sure it is worth it?

  malynx 01:01 29 Jan 2013

Hi Number six.

I've just found the information I was after regarding the video card RAM, and from what I understand, a small amount of the VRAM (256MB) is mapped into the RAM address space. However, with Windows XP, when a game or 3D application is being run all of the VRAM needs to be duplicated onto the system RAM. This quite dramatically reduces the RAM available (for 2GB - (256 + 512) = 1280MB (NB/ this doesn't include how much the system already takes).

I think that is relevant to whether it's worth it: since our Xbox broke, my wife bought me a couple of games in PC format at Christmas. I'm a long way off being able to afford a new PC, but I can spare a little if it will extend the gaming performance of my system.

But of course I don't want to be spending more than I need to, and the money could be spent elsewhere such as towards a new Xbox.

Do I understand the following correctly: 1) that a 32-bit system has a maximum possible memory space of 4 GB. 2) those 4 GB of address space are effectively reduced to approx. 3.4 GB. 3) this is due to the operating system reserving a certain amount of memory space. (?) 4) if 3 is correct, does this mean that the current 2 GB I have installed is actually reduced likewise? (If so, 4GB of RAM might show up as 3.4 GB but the "missing" RAM is still actually being used, no? And if I had 3GB of RAM I wouldn't be able to use the full 3 GB either?) 5) If a game requires 2GB RAM, then I would need just 3GB RAM to play efficiently? 6) That there would be no advantage of 4GB of RAM for such a game?

  Fruit Bat /\0/\ 10:49 29 Jan 2013

XP can only see and use a total of 3.4G (includinng graphic card)

in your case only worth adding a 1G stick

  alanrwood 10:59 29 Jan 2013


  1. No a Windows 32 bit system can address a max of around 3.4GB, the rest is wasted.
  2. The reduction is correct but from 3.4 not 4 GB.
  3. Correct
  4. Yes that is happening now with your 2GB.. No the additional RAM above 3.4GB can not be addressed at all under any circumstances. That is a restriction placed in a 32 bit operating system by Microsoft many years back so that business user would buy an operating system without this restriction. It is not a hardware restriction it is solely there because MS decreed it so. If you installed just 3GB then your effective working RAM would be reduced from 3GB to take account of the mirroring of video RAM into system RAM. Put simply, the main processor produces the data for the video card to process so requires a piece of system RAM in order to contain the data which is then passed to the video card.
  5. I believe the RAM quote takes the Video RAM into account but I can't be certain on that as it is a specification given by a company and it could vary I suppose between different games producers.
  6. Having extra RAM within the spec of the operating system, will always have some effect as that is the working area of the computer however it is not always that great when you get near to the maximum allowed. I would think that the difference in your specific case would be marginal.
  malynx 12:20 29 Jan 2013

Thank you very much for all the advice and answers, especially to Alanrwood.

It's all making a lot more sense now :)

I think I will likely add 2 x 512MB sticks in an attempt to compensate for the RAM that's lost by duplicating the VRAM.

  alanrwood 13:44 29 Jan 2013

That's what I would do considering the current price of DDR RAM. Some might say it is cheaper to get a new motherboard and DDR3 RAM provided all your other cards are compatible.

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