[filmscanners] RE: Digital Darkroom Computer Builders?

["Paul D. DeRocco" <pderocco@ix.netcom.com>]

The x86 chips have a 46-bit segmented address space which funnels into a
32-bit virtual address space, which then expands into a paged physical
address space which is somewhat larger, depending upon the chip. The only OS
that exploits segmentation that I'm aware of is Intel's iRMX. Windows and
all the Unix variants don't use segmentation at all, so all addresses
visible to the software, no matter what the addressing mode, are mere 32-bit
virtual addresses. The only way to keep larger amounts of data in RAM in
such an OS is to give part of the data to a separate process which has its
own separate 32-bit address space, or to have the OS explicitly bank switch
different data into the 32-bit address space at different times (e.g., by
remapping memory-mapped files). The only purpose of the larger physical
address space is to allow multiple huge processes or memory-mapped files to
reside in physical RAM at the same time.

Obviously, this isn't the case in the 64-bit versions of Windows for the
Alpha and the Itanium.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@ix.netcom.com

> From: Austin Franklin
>
> Correct, AND depending on addressing mode, it could be a relative address,
> so it could be anywhere in any space.  AND...no user process (on
> Windows NT
> architecture OSs anyway) addresses memory directly, it has to go through a
> logical to physical translation process.

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