In article
<local.mail.freebsd-hackers/[EMAIL PROTECTED]>
you write:
>Hi
>
>Go to http://www.uspto.gov/patft/, search for patent number 5873127, and
>you will find the description of mapping page table entries into virtual
>memory via one page directory entry pointing to the page directory itself
>- exactly what FreeBSD does with PTDPTDI and APTDPTDI entries on i386.
>(including using alternate space as in get_ptbase() in i386/pmap.c to
>access page table entries of different processes).
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.
(Not that I've read the patent, but typically the invention must meet
*ALL* the claims being described; one small deviation and it is
considered to be different.)
--
Jonathan
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message
