32bit Windows is Not Limited to 2GB/4GB

I've just seen another blog post that talks about the Windows 4GB memory limit

Here is a link to a series of posts on Raymond Chen's excellent blog that explains this in detail, I'm posting this link here so I'll have quick access to it the next time I read about the 2/4 GB limit.

http://blogs.msdn.com/oldnewthing/archive/2004/08/22/218527.aspx

The short version, address space is not the same as virtual memory is not the same as virtual memory.

On 32bit systems a single process (not the entire system) is limited to a 4GB Address Space (not memory) (and it can use only 2GB out of it, the other 2GB belongs to the kernel) but each process gets its own private address space – so if you run more then one program each has its own private address space with each own private useable 2GB (an another shared 2GB for the kernel) so with just 4 programs you get a whopping 10GB of usable memory.

If you read the linked posts you will see a process can even use more memory then fits in the address space – it's just more work to write it.

The maximum amount of memory 32bit Windows can use it between 16GB and 128GB depending on your hardware and configuration.

posted @ Tuesday, July 24, 2007 10:13 AM

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