On Mon, Jun 11, 2001 at 05:37:56PM -0500, Jonathan Lemon wrote:
> Hmm, let's see:
>
> Assignee: Digital Equipment Corporation (Maynard, MA)
> Appl. No.: 646734
> Filed: May 3, 1996
>
> Versus:
>
> * Derived from hp300 version by Mike Hibler, this version by William
> * Jolitz uses a recursive map [a pde points to the page directory] to
> * map the page tables using the pagetables themselves. This is done to
> * reduce the impact on kernel virtual memory for lots of sparse address
> * space, and to reduce the cost of memory to each process.
> *
> * from: hp300: @(#)pmap.h 7.2 (Berkeley) 12/16/90
> * from: @(#)pmap.h 7.4 (Berkeley) 5/12/91
>
> So it looks like we have prior art by around 6 years, which would
> invalidate the patent iff it was the same thing.
[rummaging through my old box of manuals... Aha!]
This also appears to be _very_ similar to the scheme described by
Intel themselves in a skinny little book entitled "80386 System
Software Writer's Guide", ISBN 1-55512-023-7, Intel order number
231499-001. This book is dated 1987 and describes the handy recursive
page table mapping starting at the bottom of page 2-18.
-Brian
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