[LCP]address space

[Erik Mouw]

On Tue, Feb 19, 2002 at 10:55:22AM -0800, Angus Mackay wrote:
> the intel pentium pro and up (don't know if any AMD's) support 36 bit memory
> addressing.

Yes, that's the PAE extension. Try "grep pae /proc/cpuinfo" to find out
if your CPU supports it.

> this allows machines with up to 64GB of ram, of course each process can only
> have a 4GB address space but you can have lots of processes with 4GB of memory
> allocated (actually I think it is still 2-3GB as the kernel is mapped in to the
> upper part of the address space). I thought that newer kernels supported this
> functionality (windows NT does) but I am not sure.

Depending on the kernel configuration, you can currently have a 3GB
userspace (on 80x86). There are people working on a 3.6GB userspace,
though, but that's the maximum you can get (I can't see how winnt can
give the full 4GB to userland, but that's off-topic).

> these machines are generally hyper expensive though and only really
> from Compaq (they usually have 4 or 8 cpus too).

If you need it, you really want a 64 bit machine. Much cleaner, much
faster, and probably as expensive.


Erik

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty
of Information Technology and Systems, Delft University of Technology,
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Fax: +31-15-2781843  Email: J.A.K.Mouw at its.tudelft.nl
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