Max memory Windows can use?

[Array]

4 gigs

I think it has more to do with the x86 architecture than it does the operating system.

[lesterc]

well it's 4 gb since that is max of your motherboard anyways
until the 64bit chips comes out and it will be able to double that easily

[sumatra]

array is (almost) right, thought its not much the architecture rather than 32bit OSes that are limited to <4gb of ram.
Although some hacks exists on industry, so, although w2k pro and w2k server are limited to 4gb, w2k advanced server & w2k datacenter versions are up to 8 & 16gb(if i remember correctly).
Of course even if you do have, lets say 8gb, you still cant allocate more than 4gb to one process (such as a real 64bit OS would do)

A similar hack is used from panther version of OSX in order to see the extented ram till OSX turns to 64bit.

[Thalaxis]

The wackiness is in the fact that even though there is no reason
other than a default parameter, Windows reserves 2 GB for each
process for system stuff. In effect, that limits processes to 2 GB
of memory.

There is a boot flag (/3GB) that allows you to override this, but I'm
not certain about which versions of Windows support it.

[ZrO-1]

Everything above is pretty much right-on. I'll just add in my 2 cents ;) .

The maximum physical addressable limit for all 32-bit systems is 4,294,967,296 bits (2^32) which is 4 gigabytes. The hack mentioned about Win 2K advanced/datacenter server is that they have the arcitecture set up so that each processor can access it's own 4GB of memory (8GB in dual proc, 16GB in 4-way).

It's also correct that Windows can't use >2GB unless the /3GB flag is set. I believe (but am not positive) that Win 2K and Win XP can set this flag automaically during setup. I do know that only Win 2K and Win XP have this flag. Win 9X and NT do not have that ability.
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:wise:
Just to throw this in for fun, the maximum physical addressable limit for 64-bit systems is 18,446,744,073,709,551,616 bits (2^64) which is 16 exabytes (17,179,869,184 gigabytes) :eek: . Now obviously 64-bit OSs don't actually address this much memory. They are actually using something like 40-bit addressing, which lets them address up to 1,099,511,627,776 bits, or 1 terabyte of memory.

And, just incase you are wondering how I came up with "exabyte", the prefixes run like this:
kilo-, mega-, giga-, tera-, peta-, exa-, zetta-, yotta-

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