Ex parte Stewart et al.

Board of Patent Appeals and Interferences

Mar 25, 1998

08094651 (B.P.A.I. Mar. 25, 1998)

Application for patent filed July 19, 1993. According to appellants, this Application1
is a continuation of Application 07/807,950, filed December 10, 1991, now U.S. Patent No.
5,239,635, granted August 24, 1993, which is a continuation of Application 07/202,886, filed
June 6, 1988, now abandoned.
1
THIS OPINION WAS NOT WRITTEN FOR PUBLICATION
The opinion in support of the decision being entered today (1) was not written for
publication in a law journal and (2) is not binding precedent of the Board.
Paper No. 20
UNITED STATES PATENT AND TRADEMARK OFFICE
_____________
BEFORE THE BOARD OF PATENT APPEALS
AND INTERFERENCES
_____________
Ex parte ROBERT E. STEWART,
TIMOTHY E. LEONARD
and SHERRY TSI-CHUAN LEE
_____________
Appeal No.96-0258
Application 08/094,6511
______________
ON BRIEF
_______________
Before KRASS, BARRETT and CARMICHAEL, Administrative Patent Judges.
KRASS, Administrative Patent Judge.
DECISION ON APPEAL
This is a decision on appeal from the final rejection of claims 13 through 15, the
only claims pending in the application.
Appeal No. 96-0258
Application 08/094,651
2
The invention pertains to page tables in a virtual memory. More particularly, a
mechanism is provided to translate virtual addresses to physical addresses by using the
virtual addresses of page table entries. A page table prototype value, representative of an
offset between the physical address and the virtual address of any particular page table
entry, is stored in a register. Because consecutive pages of the page table in virtual
memory reside in consecutive page frames in physical memory, the page frame number of
the page table entry prototype is equal to the page frame number of the first page of the
page table minus the virtual page number of the first page of the page table. The page
frame number of the page table entry prototype is a fixed offset which may be added to
the virtual page number of the virtual address of any one particular page table entry to
yield the page frame number of the physical address of the particular page table entry.
Representative independent claim 13 is reproduced as follows:
13. A method for loading a translation buffer of a computer system, which
computer system includes a virtual memory space having data referenced by virtual
addresses and a physical memory space having data referenced by physical addresses;
certain ones of the virtual addresses each having a corresponding physical address, the
translation buffer being loaded with predetermined portions of preselected virtual
addresses and predetermined portions of corresponding physical addresses, the method
comprising the steps of:
a) providing a page table memory space in the physical memory space, the page
table memory space being referenced by physical addresses which locate locations
containing at least a page table entry for a preselected page of the virtual memory space,
the page table entry indicating a physical address of the preselected page of the virtual
memory space;
b) the page table memory space further referenced by a set of virtual addresses,
Appeal No. 96-0258
Application 08/094,651
A rejection of the claims under double patenting of the obviousness type has been2
withdrawn by the examiner in view of an acceptable terminal disclaimer and is no longer
before us on appeal.
3
which correspond to the physical addresses, for referencing the page table memory space;
c) providing a page table prototype mechanism including known cross reference
information between the set of virtual addresses, and the corresponding physical addresses
for referencing the page table memory space, the known cross-reference information
comprising offset information between the certain ones of the virtual addressees and their
corresponding physical addresses;
d) operating the computer system to load information identical to a preselected
portion of the page table memory space into the translation buffer, which loading of the
translation buffer is implemented by utilizing the page table prototype mechanism to
dynamically generate physical address information for referencing the page table memory
space from a corresponding one of the set of virtual addresses and the known cross
reference information contained in the page table prototype mechanism.
The examiner relies on the following reference:
Sawada et a l. (Sawada) 4,628,451 Dec. 9, 1986
Claims 13 through 15 stand rejected under 35 U.S.C. § 103 as unpatentable over
Sawada.2
Reference is made to the brief and answer for the respective positions of appellants
and the examiner.
Appeal No. 96-0258
Application 08/094,651
4
OPINION
We will reverse as the examiner has clearly failed to present a prima facie case of
obviousness with regard to the claimed subject matter.
The examiner applies Sawada to the instant claims as set forth on pages 4-7 of the
answer and then admits [answer, page 7] that Sawada does not expressly disclose the page
table prototype mechanism including the “offset information” limitation for providing
known cross-reference information between the virtual to physical addresses. The
examiner contends, however, that the table look-up mechanism 12 of Sawada “performs
the substantially identical claimed function of providing cross reference between the virtual
to physical address information” [answer-page 7]. Apparently, the examiner bases this
finding on the disclosure, by Sawada, at column 4, lines 3-5, that “the desired page is
searched in the address translation table 3 stored in the main memory with the aid of a
table look-up mechanism 12… ” Therefore, the examiner concludes, at page 8 of the
answer, “it would have been obvious… to use a specific type of information such as offset
information for referencing virtual to physical addresses in the Sawada’s system.”
The mere fact that the look-up table 12 in Sawada “aids” in the translation of
Appeal No. 96-0258
Application 08/094,651
5
logical addresses to real addresses does not, necessarily, lead to a teaching of providing
the “offset information” claimed. We agree with appellants [page 13 of the brief] that
claim 13 does not merely provide cross reference between the virtual to physical
information but, rather, it recites “providing a page table prototype mechanism including
known cross-reference information… comprising offset information… ” We find no such
teaching or suggestion in Sawada. The claimed offset information is used to derive
physical address information from virtual address information. There is nothing in Sawada
to suggest that the type of “aid” offered by the table look-up is offset information used to
derive a physical address from a virtual address. The table look-up mechanism 12 of
Sawada does not even appear, from Figure 3, to receive physical address information,
receiving, instead, the output of comparison circuit 5 which receives, in part, information
from the logical, or virtual, address register 1. Therefore, it is difficult to see how Sawada
can be said to suggest the provision of a page table prototype mechanism including known
cross-reference information comprising offset information between certain ones of the
virtual addresses and their corresponding physical addresses, as claimed.
Appeal No. 96-0258
Application 08/094,651
6
Independent claim 14 contains similar language.
The examiner’s response to appellants’ arguments includes statements that
appellants’ arguments lack supporting facts in that appellants point out the claimed
limitations “without supporting why the reference does not teach the claimed
limitation” [answer-pages 8-9]. The initial burden is on the examiner to establish, with
evidence, that the claimed subject would have been obvious within the meaning of 35
U.S.C. § 103. Until the examiner establishes a prima facie case of obviousness, Appellants
are under no burden to show why the reference does not teach the claimed invention.
Further, the examiner responds to appellants’ arguments as to why the instant
claimed invention patentably distinguishes over Sawada by contending that the use of
“known cross-reference information comprising offset information between the certain
ones of the virtual addresses and their corresponding physical addresses” was well known
to artisans. In support of this allegation, the examiner identifies three U.S. Patents
[Anthony and Ozawa at page 9 of the answer and Chang at page 11 of the answer]. If the
examiner is relying on these references in any way to support the rejection, there would
Appeal No. 96-0258
Application 08/094,651
7
appear to be no excuse for not positively including the references in the statement of the
rejection. In re Hoch, 428 F.2d 1341, 1342 n.3, 166 USPQ 406, 407 n.3 (CCPA 1970).
Accordingly, we will not consider these references.
The examiner’s decision rejecting claims 13 through 15 under 35 U.S.C. §103 is
reversed.
REVERSED

ERROL A. KRASS )
Administrative Patent Judge )
)
)
LEE E. BARRETT ) BOARD OF PATENT
Administrative Patent Judge ) APPEALS AND
) INTERFERENCES
)
)
JAMES T. CARMICHAEL )
Administrative Patent Judge )
Appeal No. 96-0258
Application 08/094,651
8
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