Subject: Re: savecore_flags="-z"
To: None <,>
From: Wolfgang Solfrank <>
List: tech-kern
Date: 12/02/1999 22:19:02

> > >even on machines with 32 bit addressing you could swap ... not all
> > >that that memory is going to mapped into one process...
> > 
> > of course not, no.  but how can you can address more than 4gb on a 32
> > bit machine?  really big page tables?
> yup.
> While our pmap doesn't support it, recent x86 processors (Pentium Pro
> and Pentium II) support a page table format extension which allows use
> of 36-bit physical addresses (although the virtual address space per
> process is still limited to 32 bits).

This is totally orthogonal.

The question was whether you may get to swap with 4GB on a 32bit machine.
Of course you can.

The virtual address space of _one_ process (or the kernel for that matter)
cannot exceed 4GB, as is the case with the physical address space
(your observation of larger physical address spaces notwithstanding).

However, there can be more than one process on the machine (and there
normally _is_ with NetBSD :-)).  And the combined virtual address spaces
of all process may well exceed 4GB.

ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800