Does anyone know how much RAM is supported by Windows XP?  I'm looking to get a new laptop and was thinking 4 GB of RAM, however, while customizing one over at Gateway's site, it said: [quote]Microsoft Windows XP recognizes a maximum of 3GB memory.[/quote]
If that's the case, there's no reason to get 4 GB of memory.  But I don't see any reason for a 3GB restriction, so if anyone could shed some light on the issue, I'd appreciate it.

That's a stupid misunderstanding of concepts on Gateway's behalf.

WinXP supports a maximum of 3GB addressing space (when the kernel is started with "/3GB" in boot.ini) for user mode processes. So, one process can't address more than 3GB in its virtual memory address space.

However, the system can have much, much more memory that the operating system can make use of. In the IA-32 architecture (the recent versions of x86) with PAE extensions, the physical memory has a 36-bit address space, allowing up to 64 GB.
I searched a bit and this is actually not available in XP (only 2000 and 2003), so in XP you can go up to 4 GB RAM, but not beyond.

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx
http://support.microsoft.com/kb/283037/en-us

Anyway, since you don't want more than 4 GB, PAE doesn't apply to you. You can use 4 GB and Windows will use that much

Plus, you can always upgrade to Vista.

[quote author=TehUser link=topic=15600.msg157273#msg157273 date=1156792438]
Does anyone know how much RAM is supported by Windows XP?  I'm looking to get a new laptop and was thinking 4 GB of RAM, however, while customizing one over at Gateway's site, it said: [quote]Microsoft Windows XP recognizes a maximum of 3GB memory.[/quote]
If that's the case, there's no reason to get 4 GB of memory.  But I don't see any reason for a 3GB restriction, so if anyone could shed some light on the issue, I'd appreciate it.
[/quote]
As Yoni pointed out and the Microsoft pages outlined, the 3gb limit is virtual addressing space, and applications have to be linked specially to get 3gb, or else by default they get 2.

I can't imagine any application that could use 3gb of RAM short of intensive medical applications or highly sensitive things of that sort (perhaps video editing tools or perhaps enterprise databases that have hundreds of tables and millions of rows.  So all told, you're looking at rare instances of even using that much.

Still, I'd jump at 4gb of RAM.

[quote author=MyndFyre[vL] link=topic=15600.msg157287#msg157287 date=1156815126]
I can't imagine any application that could use 3gb of RAM short of intensive medical applications or highly sensitive things of that sort (perhaps video editing tools or perhaps enterprise databases that have hundreds of tables and millions of rows.  So all told, you're looking at rare instances of even using that much.
[/quote]

Any sort of scientific computing?  Of course, most would never dream of doing that in
Windows XP / Vista.

You need 4GB of RAM? Holy shit.

RAM goes pretty fast when you start running things that don't share nicely, such as VMs.  This primarily applies to full blown virtual computers (i.e. guest systems running inside VMware / VirtualPC), but so-called Java VMs and CLR VMs are also pretty memory intensive for what they give you.