Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

This MSDN article lists the virtual address space limits for current versions of Windows.

I notice that for 32 bit systems the address space is divided into 2 GB user and 2 GB kernel, which makes sense. Likewise on amd64 systems the (presumably 44 bit) address space is divided into 8 TB user space and 8 TB kernel space.

But ia64 has 7 TB user space. Is this an arbitrary limit or is it because the system uses 9 TB for the kernel space or why is this?

share|improve this question
I'm sure the nerds in SO or SF know the answer to this. – surfasb Feb 11 '12 at 2:55
up vote 4 down vote accepted

Mark Russinovich explains it here:

It turns out that the difference is centered in a Windows specific feature. For IA64, the top 1TB of the 8TB memory-space is reserved for wow64 mappings. Wow64 is the feature that allows running 32-bit code on a 64-bit system. The reason that X64-64 (a.k.a. amd64) doesn't have it, is that it is ISA-compatable so just need the right libraries to run.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .