On 22 Sep 99, at 8:54, Walter R. Worth wrote:

>  The default AGP aperture size is 64MB, a setting that  accommodates both
> Windows* 9x and NT* 5 environments.

> Although Windows 9x provides a larger memory space (2GB virtual
> memory addressing), NT 5 has more limited system memory resources.

  This statement is, I think, confused.  Both 9x and NT provide each
process with a 4GB virtual address space[*], the range that can be
spanned by a 32-bit "flat" pointer.  [The *total* virtual memory
space is much larger.]
  However, the AGP aperture is not some abstract region in virtual
memory; it is a dedicated range of physical memory.  As such, it has
to lie within the *physical* address space of the CPU -- and of the
chipset.  [While few current motherboards provide sufficient physical
SIMM/DIMM slots for so much RAM, typical current chipsets are limited
to 1 or 2 GB of total physical memory.  So while "2GB" does figure
into this, it's not at a level where it has anything to do with how
the OS arranges virtual memory.]

[*] NT and 9x divide up this 4GB space slightly differently, but the
details don't matter to this discussion.

David G

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