On using 4 GB ram under XP Pro

Factual Questions
1

I understand that Windows XP can only address a maximum of 2GB of RAM (if that’s not true, please correct me).

But if I load up my box with 4GB, can I use the other 2 GB in some productive and straightforward manner, such as with a RAM drive or something? If so, and I’m just a general XP user, what could I readily “store” in the RAM drive – virtual memory or something else?

Thanks!

2

The amount of RAM available to XP Pro depends on the BIOS of the machine. With 4Gb installed, you’ll get anywhere from zero to almost all 4G of memory available to your machine. (Yes, you can get less than two. On some systems memory over 2G will actually subtract from total memory, byte for byte).

If it doesn’t see it all, you can look for a BIOS upgrade for your system, but otherwise, no, you can’t use it for anything.

You can, however, upgrade to an OS that can see it (XP-64 or Vista 64), assuming the CPU is 64-bit.

3

So corrected. XP Pro can address up to 4 GB.

4

3.5, actually. Virtual memory (which uses free hard drive space) can’t really compare to the real thing - if you’re pinched for motherboard space, check to see if you can support duel-channel RAM - in which two identical sticks are used simultaneously as opposed to in series. This can give you some more “bandwidth” to work with.

5

WinXP can use more than 2GB of RAM. Here’s a link from MS:

http://support.microsoft.com/kb/291988

And another random article (google “4gb windows xp” for a slew of them):

http://members.cox.net/slatteryt/RAM.html

I have 4GB in my XP box - if I check the system properties, Windows says that I only have 3GB. Basically the extra memory extends into address space used by XP for other functions so you can’t get at it easily.

This doesn’t mean that 4GB is a bad idea - for starters if you are using matched sets of RAM (2x2gb or 4x1gb) your motherboard may be running them in dual channel mode (basically it reads and writes to RAM twice as fast).

And when/if you move to a 64-bit OS you’ll see all 4GB (I don’t recall the maximum memory that a 64-bit OS can address off the top of my head but it’s substantially larger than 4GB).

6

Any 32bit system can only handle a total of 4 GB but effective is usually between 3.2 and 3.5GB. A 64-bit OS can handle as much as you can throw in it.

7

Thanks for the quick and helpful replies, everyone!

I new there was a 32-bit address space, but I wasn’t sure XP didn’t reserve a bit, as I had been previously mis-informed.

I’ve got a new Intel DQ35MP (don’t ask why) and so with your information, I can be confident of usefully employing more than 3 GB.

Thanks again

8

I don’t know the capabilities of that chipset. You may want to verify. It could be that you’re in for some bad news.

9

Thanks, but can you explain why you linked to a Mac article?

Here’s an Intel link: DQ35MP Memory

10

Perhaps you were referring to the same issue mentioned above regarding a limit of around 2/2.3 GB? Or the part where the Mac article mentioned that some high-end gamers’ boxes with large graphics memory wouldn’t support much more than 2 GB?

I don’t have any games, and consequently all my graphics cards have a small memory footprint.

Or were you referring to something else?

11

You weren’t misinformed. The original design of NT split the address space in half. Half was user address space, half was system address space. This boundary has been tweaked upwards in later releases, but it’s still there.

12

Since we’re in GQ, I’ll point out that this is not quite correct. 32 bit Intel CPUs have long been able to use a technology called PAE to address up to 64 GB.

13

I think there’s some confusion here between a process’s virtual address space and physical memory. Each process may be limited to 2GB or 3GB of its 4GB address space, but different processes will use different parts of physical memory. Therefore, leaving aside things like BIOS limitations, Windows XP can make use of up to 4GB RAM directly. Some of it will be used by the OS itself, sure, but it’s not like there’s a fixed area of physical memory that processes can’t use.

14

I stand corrected. :slight_smile:

15

One further point for the OP: there is, in fact, a 64 bit version of XP, which is not constrained by the 4 GB limitation, though it does have a 128 GB limitation.

16

It wasn’t a Mac-only article. :confused: