United States Court of Appeals 

for the Federal Circuit ______________________

ATI TECHNOLOGIES ULC,

Appellant

v.

ANDREI IANCU, UNDER SECRETARY OF 

COMMERCE FOR INTELLECTUAL PROPERTY 

AND DIRECTOR OF THE UNITED STATES 

PATENT AND TRADEMARK OFFICE,

Intervenor

______________________

2016-2222, 2016-2406, 2016-2608

______________________

Appeals from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in Nos. IPR2015-

00325, IPR2015-00326, IPR2015-00330.

______________________

Decided: April 11, 2019

______________________

AARON ROBERT FAHRENKROG, Robins Kaplan LLP, 

Minneapolis, MN, argued for appellant. Also represented 

by BRYAN MECHELL; DANIELLE ROSENTHAL, New York, NY.

THOMAS W. KRAUSE, Office of the Solicitor, United 

States Patent and Trademark Office, Alexandria, VA, argued for intervenor. Also represented by FARHEENA 

YASMEEN RASHEED, ROBERT J. MCMANUS.

______________________
2 ATI TECHNOLOGIES ULC v. IANCU

Before NEWMAN, O’MALLEY, and WALLACH, Circuit 

Judges.

NEWMAN, Circuit Judge.

ATI Technologies ULC (“ATI”) appeals three final decisions of the Patent Trial and Appeal Board (“PTAB” or 

“Board”) on petitions for Inter Partes Review filed by LG 

Electronics, Inc. (“LGE”).1 The Board held all but one of 

the challenged claims unpatentable as anticipated or obvious, invalidating claims 1, 2, and 5–7 of U.S. Patent No. 

7,742,053 (“the ’053 patent”); claims 1–3, 5, 6, 8–11, 13, 15,2

17, and 18 of U.S. Patent No. 6,897,871 (“the ’871 patent”);

and claims 1 and 2 of U.S. Patent No. 7,327,369 (“the ’369 

patent”). Claim 20 of the ’871 patent was held patentable.

The three patents are called the “Unified Shader Patents.”

Petitioner LGE cited references against each of the 

Unified Shader Patents, and ATI’s response was that the

invention in each of the three patents preceded the primary 

reference dates for that patent. In conformity with 37 

C.F.R. § 1.131 (“Rule 131”), ATI presented evidence of conception, reduction to practice, and diligence for each patent. The PTAB held separate trials, and received 

testimony and argument from both sides. The antedating 

 

1 LG Electronics, Inc. v. ATI Techs., No. IPR2015-

00325 (PTAB April 14, 2016) (“the ’053 Op.”); LG Electronics, Inc., v. ATI Techs., No. IPR2015-00326 (PTAB June 28, 

2016) (“the ’871 Op.”); LG Electronics, Inc., v. ATI Techs.,

No. IPR2015-00330 (PTAB July 1, 2016) (“the ’369 Op.”). 

The cases were consolidated for this appeal. LG Electronics withdrew from the appeal and withdrew its cross-appeal, and the PTO Director intervened in support of the 

three PTAB decisions.

2 Claim 15 of the ’871 patent is not challenged on appeal.
ATI TECHNOLOGIES ULC v. IANCU 3

issue was treated in detail in the ’053 opinion, and applied 

to the ’871 and ’369 patents in separate opinions.

For all three Unified Shader Patents, the PTAB held 

that conception was established before the primary reference dates, and that constructive reduction to practice occurred on the filing date of each patent. However, the 

PTAB held that ATI had not established actual reduction 

to practice and had not established diligence to constructive reduction to practice, for all three patents. The PTAB

then invalidated the Unified Shader Patents based on the 

cited references.

We conclude that the PTAB erred in its application of 

the law of diligence, and that on the correct law, diligence 

was shown, thereby antedating the relevant references. 

The PTO’s decisions of unpatentability are reversed.

The technology

A “shader” as used in this field is a computer-implemented system that specifies how a computer-graphics 

three-dimensional image is generated and presented on a 

two-dimensional screen. The prior art describes that computer-graphics images are drawn on a screen by filling in a 

grid of dots called “pixels.” Shapes are represented by a 

collection of simple polygons such as triangles or squares, 

called “primitives,” formed by the interconnection of pixels. 

The corner of each primitive is called a “vertex,” with each 

vertex defined by the spatial coordinates: x, y, and z.

Color and texture are applied to the individual pixels 

that comprise the shape, based on the location of the pixels 

within the primitive and the primitive’s orientation relative to the generated shape. To orient the wireframe threedimensional model, matrix transformations applied to vertices Vx, Vy, and Vz of the primitives generate new vertices 

Vx’, Vy’, and Vz’, which are then translated into pixels. The

graphics processor interconnects the primitives and applies color and texture to the generated shapes. ATI 
4 ATI TECHNOLOGIES ULC v. IANCU

presented the following illustration of the graphics of display of a three-dimensional object as a two-dimensional image:

Dr. Wolfe Decl. at ¶¶ 44–45 (J.A. 5200–01); see ’871 patent, 

col. 1, ll. 11–60.

Prior art processors required separate shaders to specify how and with what attributes a final image is drawn, in 

transforming primitives by adjusting the x, y, and z coordinates of their vertices. Prior art graphics processors required both a vertex shader and a pixel shader, because 

vertex operations and pixel operations have different processing requirements and were required to be performed 

separately and sequentially by separate shader systems. 

The Unified Shader Patents describe novel systems that 

perform both vertex operations and pixel operations, 

thereby providing enhanced efficiency, reliability, and 

speed.

Following is an outline of the Unified Shader Patents, 

and representative claims on appeal: 
ATI TECHNOLOGIES ULC v. IANCU 5

The ’053 patent, inventors Laurent Lefebvre, 

Andrew E. Gruber, and Stephen L. Morein, 

filed Sept. 29, 2003

The ’053 patent is the first-filed of the Unified Shader 

Patents. It describes a multi-thread (unified) graphics processing system that processes both vertex and pixel operations. The system employs a memory device for storing 

command threads and an arbiter for providing a command 

thread to a command processing engine, based on a priority

plan whereby the command processing engine performs either vertex or pixel operations based on the command 

thread from the arbiter. The specification provides details 

of the system and its operation. Claim 5 was deemed representative for the ’053 patent:

5. A graphics processing system comprising:

at least one memory device comprising a first 

portion operative to store a plurality of pixel command threads and a second portion operative to 

store a plurality of vertex command threads;

an arbiter, coupled to the at least one memory 

device, operable to select a command thread from 

either of the plurality of pixel command threads 

and the plurality of vertex command threads; and

a plurality of command processing engines, 

coupled to the arbiter, each operable to receive and 

process the command thread.

The PTAB cited three primary references against the ’053 

patent: U.S. Patent No. 7,363,472 (“Stuttard”) having an 

effective filing date of October 9, 2001; U.S. Patent No. 

7,015,913 (“Lindholm”) having an effective filing date of 

June 27, 2003; and U.S. Patent No. 7,233,335 (“Moreton”)

having an effective filing date of April 21, 2003.

ATI presented evidence of conception before the earliest reference filing date of October 9, 2001 (Stuttard), and 
6 ATI TECHNOLOGIES ULC v. IANCU

evidence of continuing activity until the ’053 patent’s effective filing date of September 29, 2003. The PTAB held that 

“ATI has demonstrated by a preponderance of the evidence 

that the named inventors of the ’053 patent conceived the 

claimed system no later than August 24, 2001, prior to the 

U.S. filing dates of Stuttard, Moreton, and Lindholm.” ’053 

Op. at 16–17. The dates of conception and constructive reduction to practice are not disputed on appeal.

However, the PTAB held that diligence and actual reduction to practice had not been shown, and on this basis 

the PTAB held claims 1, 2, and 5–7 of the ’053 patent unpatentable on the following grounds: (1) claims 5–7 as anticipated by the Moreton reference; (2) claims 1 and 2 as 

obvious over Moreton combined with Whittaker (U.S. Patent No. 5,968,167); (3) claims 1, 2, and 5–7 as obvious over 

Lindholm in view of Admitted Prior Art; and (4) claims 1, 

2, and 5–7 as obvious over Stuttard in view of Admitted 

Prior Art.

LGE has withdrawn from the appeal, and the PTO Director has intervened and argues in support of the PTAB’s 

holdings that diligence and actual reduction to practice 

were not established, and thus that the references were not 

antedated.

The ’871 and ’369 patents, inventors Steven 

Morein, Laurent Lefebvre, Andy Gruber, and 

Andi Skende, filed November 20, 2003

The ’871 and the ’369 patents have a common specification and priority filing date of November 20, 2003. Both 

patents are directed to a graphics processor employing a 

unified shader capable of performing both vertex operations and pixel operations, and describe and claim specific 

embodiments. Figure 4A is a schematic of the overall process, and is included in ’871 and the ’369 Patents:
ATI TECHNOLOGIES ULC v. IANCU 7

As described in the patents, the graphics processor 60 includes a multiplexer 66 with a first and a second input, 

whereby vertex data are provided at a first input, and interpolated pixel parameter data and attribute data from a 

rasterization engine 74 are provided at a second input. The 

arbiter 64 generates a control signal that is transmitted to 

the multiplexer 66, determining the inputs transmitted to 

the unified shader 62.
8 ATI TECHNOLOGIES ULC v. IANCU

Lindholm is the only primary reference cited against 

the ’871 and ’369 claims on appeal.

The ’871 patent

The ’871 patent adds to the ’053 patent the structural 

elements of a unified shader architecture, including an arbiter and selector for determining which vertex or pixel inputs the unified shader will process. The shader is “more 

computationally efficient because it allows the shader to be 

flexibly allocated to pixels or vertices based on workload.” 

’871 patent, col. 2, ll. 64–67. Claim 1 was deemed representative:

1. A graphics processor, comprising: 

an arbiter circuit for selecting one of a plurality 

of inputs in response to a control signal; and 

a shader, coupled to the arbiter circuit, operative to process the selected one of the plurality of 

inputs, the shader including means for performing 

vertex operations and pixel operations, and performing one of the vertex operations or pixel operations based on the selected one of the plurality of 

inputs, wherein the shader provides a appearance 

attribute.

The PTAB again held that ATI had established conception 

before the applicable reference date, but had not established actual reduction to practice and had not established 

diligence to constructive reduction to practice, stating that 

“Patent Owner relies [on] the same evidence and substantially the same arguments in the present review and in 

IPR2015–00325 in support of its efforts to antedate Lindholm.” ’871 Op. at 3.

Thus the PTAB held claims 1, 2, 5, 8, 10–11, 13 and 15 

of the ’871 patent unpatentable as anticipated by Lindholm, claims 3 and 6 unpatentable as obvious over the combination of Lindholm and Open GL, and claims 9, 17, and 
ATI TECHNOLOGIES ULC v. IANCU 9

18 unpatentable as obvious over the combination of Lindholm and Kizhepat. The PTAB alternatively held claim 15 

unpatentable as obvious over a reference to Rich.

The PTAB held claim 20 patentable, and LGE’s crossappeal on claim 20 has been withdrawn.

The ’369 patent

The ’369 patent adds a vertex storage block to the unified shader system. The ’369 patent further generates a 

color associated with a specific pixel. Claims 1 and 2 are 

the only claims in the ’369 patent:

1. A graphics processor, comprising:

an arbiter circuit for selecting one of a plurality 

of inputs in response to a control signal;

a shader, coupled to the arbiter circuit, operative to process the selected one of the plurality of 

inputs, the shader including means for performing 

vertex operations and pixel operations, and performing one of the vertex operations or pixel operations based on the selected one of the plurality of 

inputs, wherein the shader provides a appearance 

attribute;

a vertex storage block for maintaining vertex 

information;

wherein the vertex storage block further includes a parameter cache operative to maintain appearance attribute data for a corresponding vertex 

and a position cache operative to maintain position 

data for a corresponding vertex; and

wherein the appearance attribute is color, and 

the color is associated with a corresponding pixel 

when the selected one of the plurality inputs is 

pixel data.
10 ATI TECHNOLOGIES ULC v. IANCU

2. The graphics processor of claim 1 wherein 

the appearance attribute is position, and the position attribute is associated with a corresponding 

vertex when the selected one of the plurality of inputs is vertex data.

The PTAB again held that conception and constructive reduction to practice had been established, but that actual 

reduction to practice and diligence had not been shown. On 

this ground, the PTAB held the ’369 claims unpatentable 

over Lindholm and OpenGL.

DISCUSSION

Standard of review

The PTAB’s findings of fact are reviewed for support by 

substantial evidence, and plenary review is accorded the 

PTAB’s conclusions of law. “‘[S]ubstantial evidence’ review 

involves examination of the record as a whole, taking into 

account evidence that both justifies and detracts from an 

agency’s decision.” In re Gartside, 203 F.3d 1305, 1312 

(Fed. Cir. 2000). “[T]he Board’s opinion must explicate its 

factual conclusions, enabling us to verify readily whether 

those conclusions are indeed supported by ‘substantial evidence’ contained within the record.” Id. at 1314. “That record, when before us, is closed, in that the Board’s decision 

must be justified within the four corners of that record.” Id.

Antedating a Reference — 37 C.F.R. §1.131

Rule 131 is called the “swearing back” or “swearing behind” provision. See generally Manual of Patent Examining Procedure (“MPEP”) § 715 (9th ed. Jan. 2018). It 

applies to references that may be prior art, but that do not 

claim the same invention.3 The standards for whether the 

 

3 Prior to March 16, 2013, patents or applications on 

the same invention were placed into “interference” for
ATI TECHNOLOGIES ULC v. IANCU 11

subject matter in a reference has been antedated are stated 

in Rule 131:

(a) When any claim of an application or a patent 

under reexamination is rejected, the applicant or 

patent owner may submit an appropriate oath or 

declaration to establish invention of the subject 

matter of the rejected claim prior to the effective 

date of the reference or activity on which the rejection is based.

(b) The showing of facts for an oath or declaration 

under paragraph (a) of this section shall be such, in 

character and weight, as to establish reduction to 

practice prior to the effective date of the reference, 

or conception of the invention prior to the effective 

date of the reference coupled with due diligence 

from prior to said date to a subsequent reduction to 

practice or to the filing of the application.

Accordingly, pursuant to Rule 131(b), the applicant 

bears the burden of proof to establish either: (1) prior reduction to practice; or (2) prior conception “coupled with 

due diligence.” In re Steed, 802 F.3d 1311, 1316 (Fed. Cir. 

2015). “Demonstration of such priority requires documentary support, from which factual findings and inferences 

are drawn, in application of the rules and law of conception, 

reduction to practice, and diligence.” Id. Indeed, Rule 

131(b) expressly provides that: “[o]riginal exhibits of drawings or records, or photocopies thereof, must accompany 

and form part of the affidavit or declaration or their absence must be satisfactorily explained.”

It is undisputed that ATI conceived of the patent claims 

before the primary reference filing dates. As explained 

 

determination of the first inventor. Since March 16, 2013, 

only the application with the earlier filing date is granted. 

MPEP § 2301.04.
12 ATI TECHNOLOGIES ULC v. IANCU

below, we find that ATI demonstrated diligence through 

constructive reduction to practice as to the three Unified 

Shader Patents. Given this conclusion, we need not review 

the PTAB’s rulings concerning actual reduction to practice. 

These rulings are vacated.

The Standard for Diligence

The diligence requirement implements the principle 

that, to antedate a reference, the applicant must not only 

have conceived the invention before the reference date, but 

must have reasonably continued activity to reduce the invention to practice. The court summarized the law with 

respect to “due diligence” for purposes of Rule 131:

A patent owner need not prove the inventor continuously exercised reasonable diligence throughout 

the critical period; it must show there was reasonably continuous diligence. See, e.g., Tyco 

Healthcare Grp. v. Ethicon Endo-Surgery, Inc., 774 

F.3d 968, 975 (Fed. Cir. 2014); Monsanto, 261 F.3d 

at 1370. Under this standard, an inventor is not 

required to work on reducing his invention to practice every day during the critical period. See Monsanto, 261 F.3d at 1369. And periods of inactivity 

within the critical period do not automatically vanquish a patent owner’s claim of reasonable diligence.

Perfect Surgical Techniques, Inc. v. Olympus Am., Inc., 841 

F.3d 1004, 1009 (Fed. Cir. 2016) (emphases original).

“An inventor’s testimony regarding his reasonable diligence must be corroborated by evidence.” Id. at 1007; see

Price v. Symsek, 988 F.2d 1187, 1194 (Fed. Cir. 1993). The 

burden of proving diligence is on the party asserting the 

benefit of diligent activity, in this case the benefit of the 

Rule 131 “swearing back” provision. See In re Steed, 802 

F.3d 1311, 1316 (Fed. Cir. 2015) (“Steed bears the burden 

to establish ‘facts ... in character and weight, as to establish 
ATI TECHNOLOGIES ULC v. IANCU 13

reduction to practice prior to the effective date of the reference, or conception of the invention prior to the effective 

date of the reference coupled with due diligence from prior 

to said date to a subsequent reduction to practice or to the 

filing of the application.’ 37 C.F.R. § 1.131(b)”); In re Magnum Oil Tools Int’l, Ltd., 829 F.3d 1364, 1376 (Fed. Cir. 

2016) (“[A] patentee bears the burden of establishing that 

its claimed invention is entitled to an earlier priority date 

than an asserted prior art reference.”); see also Perfect Surgical, 841 F.3d at 1007 (Fed. Cir. 2016) (“Pre–AIA section 

102(g) allows a patent owner to antedate a reference by 

proving earlier conception and reasonable diligence in reducing to practice.”); Mahurkar v. C.R. Bard, Inc., 79 F.3d 

1572, 1578 (Fed. Cir. 1996) (“Where a party is first to conceive but second to reduce to practice, that party must 

demonstrate reasonable diligence toward reduction to 

practice from a date just prior to the other party’s conception to its reduction to practice.”). “A ‘variety of activities’

may corroborate an inventor’s testimony of reasonable diligence and such corroborating evidence is considered ‘as a 

whole’ under a rule of reason.” Perfect Surgical, 841 F.3d 

at 1007–08 (quoting Brown v. Barbacid, 436 F.3d 1376, 

1380 (Fed. Cir. 2006)).

ATI stated that the PTAB applied an incorrect definition of diligence, and LGE so conceded in its brief before it 

withdrew from this appeal. The Director instead describes 

as “boilerplate” the PTAB’s erroneous definition. However, 

it was not boilerplate, for the PTAB appeared to find a dispositive difference between “continuous reasonable diligence” and “reasonably continuous diligence,” despite the 

documentary evidence of activity by ATI on “every business 

day.” We conclude that the PTAB applied the wrong legal 

standard for diligence. As explained below, under the 

proper legal standard, the record is clear that ATI exercised the requisite “reasonably continuous diligence.” See 

Perfect Surgical, 841 F.3d at 1009.
14 ATI TECHNOLOGIES ULC v. IANCU

Diligence — Declarations and Documents

Inventor Laurent Lefebvre described conception and 

activities developing the technology in the three Unified 

Shader Patents. His 60-page Declaration describes his and 

the other inventors’ and other ATI employees’ activities on 

this project (designated the R400 project), and was accompanied by “almost 1300” pages of documentary records 

showing the work done and by whom and when, including 

metadata, document logs, and folder histories. J.A. 2628–

88; J.A. 2689–3943; J.A. 3994–4312.

Mr. Lefebvre explained that as the Unified Shader project evolved, ATI increased the number of employees until 

“ATI assigned over one hundred project managers/designers to implement and test the R400 . . . [and] at least one 

person on the R400 project team worked on the R400 design every non-holiday business day.” ’053 patent Lefebvre 

Decl. ¶¶ 38–43 (J.A. 2650–54). He explained the development of the technology, and identified the records as the 

project evolved. He explained that the employees were required to save their work in a revision-control system 

called Perforce that maintains metadata, and he referenced the relevant documentary records and provided summaries of the various aspects to which employees were 

assigned, and records in document logs and folder histories.

“Metadata” are data about changes in files, source 

codes, edits, logs of access of files, time and date stamps, 

user, changes made, etc. Calvin Watson Decl. ¶¶ 7–10 (J.A. 

7906–07). The metadata include information concerning 

revisions, including who made the revision and the date 

each revision was made. ’053 patent Lefebvre Decl. ¶ 39

(J.A. 2650). Mr. Lefebvre provided a calendar summarizing the metadata documentation, showing what activities 

were performed on what dates. Id. ¶¶ 41–43 (J.A. 2654);

Section V (J.A. 2660–85) (calendar summarizing Perforce 

folder history entries).
ATI TECHNOLOGIES ULC v. IANCU 15

Mr. Lefebvre explained that ATI employees used the 

R400 Sequencer Specification to write emulation code and 

RTL [register-transfer level] code for the R400’s functional 

blocks, and testing the R400’s functional blocks. The documentation included documents recording metadata on the 

R400 Sequencer Emulator Folder History, Ex. 2048 (18 

pages) (J.A. 3994–4012); Sequencer Parts Development 

Folder History, Ex. 2049 (33 pages) (J.A. 4013–46); R400 

Document Library Folder History, Ex. 2050 (110 pages)

(J.A. 4047–4157); R400 Architecture Folder History, Ex.

2051 (26 pages) (J.A. 4158–84); and R400 Testing Folder 

History, Ex. 2052 (127 pages) (J.A. 4185–4312). Mr. 

Lefebvre stated that:

This metadata is not exhaustive of all sequencer/shader-pipe files that were edited during 

this timeframe. But this metadata shows work 

that was necessary for implementing the R400 design. Specifically, this metadata shows the design, 

development, and testing of the R400 sequencer 

and graphics blocks.

’053 patent Lefebvre Decl. ¶ 42 (J.A. 2654).

Summarizing the information in the documents, Mr. 

Lefebvre classified the ongoing activities as they applied to 

the three Unified Shader patents, for the following periods: 

(1) from prior to the Stuttard reference’s filing date of October 9, 2001 to the ’053 patent’s filing on September 29, 

2003; (2) from prior to the Moreton reference’s filing date 

of April 21, 2003 to the ’053 patent’s filing date of September 29, 2003; (3) from prior to the Lindholm reference’s filing date of June 27, 2003 to the ’053 patent’s filing date of 

September 29, 2003; (4) from prior to the Lindholm reference’s filing date of June 27, 2003 to the ’871 patent’s filing 

date of November 20, 2003; and (5) from prior to the Lindholm reference’s filing date of June 27, 2003 to the ’369 patent’s filing date of November 20, 2003. ’053 patent 

Lefebvre Decl. ¶¶ 41–43 and Part V (Ex. 2006) (J.A. 2654; 
16 ATI TECHNOLOGIES ULC v. IANCU

J.A. 2660–85); ’871 patent Lefebvre Decl. ¶¶ 41–43 and 

Part V (Ex. 2006) (J.A. 8001; J.A. 8007–34).

Mr. Lefebvre testified that “[f]or me and many of the 

other project managers/designers, the R400 was the only 

project that most of us were assigned to—it was our fulltime responsibility. . . . [and] any time that we did work for 

ATI between late 2001 and the end of 2003, that work 

would have been on the R400.” ’871 patent Lefebvre Decl. 

¶ 43 (J.A. 8001). Mr. Lefebvre further testified his “analysis [of this metadata] shows that at least one person on the 

R400 project team worked on the R400 design every nonholiday business day from early 2002 (when we conceived 

of the invention) until November 20, 2003 (the effective filing date of the ’871 patent).” Id. ¶ 41. Mr. Lefebvre states 

that he updated the R400 Sequencer Specification every 

two to three weeks as the team worked to add or remove 

data. ’053 patent Lefebvre Decl. ¶ 36 (J.A. 2649).

ATI’s expert witness, Dr. Wolfe, reviewed the records 

and summarized their content, submitting a Declaration 

and appearing as a witness before the PTAB. Dr. Wolfe’s 

testimony concentrated on actual reduction to practice, and 

included additional exhibits as well as some of the same 

exhibits (e.g., Ex. 2010), as well as mapping the RTL Code 

to the claims. Ex. 2106 (J.A. 4702–4882).

During the trial and at the final hearing the PTAB 

raised no question about any of the evidence as to any of 

the claimed inventions; nor had LGE done so. No inquiry 

was made to any witness as to any fact or date or statement 

or document. However, in its Final Written Decision the 

PTAB held that diligence had not been established as to 

any of the three Unified Shader Patents, the PTAB ruling 

that “ATI fails to provide evidence that is specific both as 

to facts and dates for each of the three critical periods.” ’053 

Op. at 43.
ATI TECHNOLOGIES ULC v. IANCU 17

The PTAB Decision 

The PTAB decision mentions two aspects as showing 

failure of proof of diligence: (1) that “Mr. Lefebvre redesigned the R400, after the conception date, to include an 

optional feature that is not recited in the claims at issue,” 

’053 Op. at 44; and (2) that “ATI fails to provide a reasonable way for us to determine whether unexplained lapses 

have not occurred.” Id. at 53.

The “optional feature” aspect was focused on a “second 

chip design,” the PTAB stating that Mr. Lefebvre had not 

provided a “meaningful explanation as to which activities 

listed in the metadata are directed to the second chip design,” ’053 Op. at 45. The PTAB criticized that “ATI’s calendar, metadata, document logs, and folder histories 

(nearly 1,300 pages) are not self-explanatory and do not explain meaningfully as to which tasks are reasonably necessary for reducing the claimed elements to practice, and 

which tasks are directed toward developing and testing 

other chip designs and optional features.” Id. at 41–42. 

The PTAB dismissed the entirety of the evidence, stating

that “work done for the entire R400 project includes developing and testing other chip designs and optional features 

to improve graphic processing systems generally, and not 

merely for the claimed elements.” Id. at 42.

The trial record shows no inquiry of any witness, asking about lapses in activity related to the Unified Shader. 

In its Final Written Decision the PTAB refers to Lefebvre’s 

information that ATI worked to increase the capability of 

the product to meet the criteria of a potential customer for 

the Unified Shader, identified as Microsoft. The PTAB appears to have held that this work defeated diligence, although the PTAB did not state or suggest that this work 

was not within the Unified Shader patents. Nor does the 

PTAB propose that any of the work documented in the 1300 

pages of exhibits is outside of the claims. Rather, the PTAB 
18 ATI TECHNOLOGIES ULC v. IANCU

complains that ATI did not identify “unexplained lapses” 

in the shader activity. Id. at 53.

Diligence is not negated if the inventor works on improvements and evaluates alternatives while developing 

an invention. In re Jolley, 308 F.3d 1317, 1328 (Fed. Cir. 

2002) (“[W]e decline to adopt a rule that evidence of diligence must be excluded if there is any possibility that it 

could be construed in support of an invention beyond the 

reach of the count.” (emphasis original)). Here, neither 

LGE (before its withdrawal) nor the PTAB points to even 

such possibility — to the contrary, Lefebvre testified that 

over 100 ATI employees worked on this project.

Mr. Lefebvre’s Declaration traced the development of 

this technology, and explained the significance of the various stages. He testified that the first “triangle test” demonstrated that they had successfully designed software that 

performed the unified shader operations, but that additional effort was required to perfect the operations. He testified that “after you are done with the single triangle you 

need to continue working . . . [because] it’s not a sign that 

you can productize a chip. In order to have something you 

can productize, you have to run these thousand other 

tests.” Ex. 1035 at 143:20–144:22 (J.A. 2060–61) (Deposition Transcript of Mr. Lefebvre).

The PTAB identified no delays, no gaps in activity. Rather, the PTAB complained that Lefebvre had not identified any “unexplained lapses.” It is correct that Mr.

Lefebvre identified daily activity, not lapses. The Director 

as Intervenor quotes the PTAB statements that ATI was 

working on “unclaimed features,” but the Director, like the 

PTAB, does not explain or identify any such features. See

Power Integrations, Inc. v. Lee, 797 F.3d 1318, 1323 (Fed. 

Cir. 2015) (the Board must “fully and particularly set out 

the bases upon which it reached [its] decision”); In re 

NuVasive, Inc., 842 F.3d 1376, 1382 (Fed. Cir. 2016) (“[T]he 

PTAB must make the necessary findings and have an 
ATI TECHNOLOGIES ULC v. IANCU 19

adequate ‘evidentiary basis for its findings.’”) (quoting In 

re Lee, 277 F.3d 1338, 1344 (Fed. Cir. 2002)).

On appeal, we are directed to no view of the evidence

that could support a conclusion that ATI set aside the development of the Unified Shader. The PTAB cited no basis 

for finding that this technology was not being diligently

pursued. The Director seeks to excuse the PTAB’s absence 

of support for its holding, by stating that ATI bears the burden of proof of diligence. However, the Director does not 

explain where the burden of proof was not met, upon the 

extensive evidence of daily activity. LGE provided no evidence to the contrary; the LGE argument was that ATI 

could have filed its patent applications at an earlier stage

of development, and that continuing activity to develop a

satisfactory product does not count as diligence. Precedent 

is not in accord; the purpose of the diligence requirement is 

to show that the invention was not abandoned or set aside. 

See Perfect Surgical, 841 F.3d at 1009 (explaining that the 

“point of the diligence analysis . . . is to assure that, in light 

of the evidence as a whole, ‘the invention was not abandoned or unreasonably delayed’”). Here, the Director does 

not point to the remotest suggestion of abandonment or setting aside of the Unified Shader technology.

The Director as Intervenor cites no support for the 

PTAB’s decisions, but merely quotes the PTAB’s statement

that the testimony of Lefebvre is “vague and not sufficiently corroborated by independent evidence,” ’053 Op. at 

42. The Director does not mention the 1300 pages of corroborative documents. Although the Director states in his

Intervenor’s brief that there is an “unexplained delay” before the ’053 application was filed, Dir. Br. 52, the Director 

does not elaborate.

Instead, the Director presses the argument that ATI 

should have filed its patent applications sooner. The Director states that: “At bottom, the problem was ATI’s failure to ‘explain why the team of engineers and designers 
20 ATI TECHNOLOGIES ULC v. IANCU

could not have designed, built, and tested a chip embodying 

the claimed elements, without those optional features,’” 

Dir. Br. 56, quoting PTAB ’053 Op. at 52–53. The Director 

states that to show diligence “the work relied on must ordinarily be directly related to reduction to practice of the 

invention.” Dir. Br. 56 (quoting Naber v. Cricchi, 567 F.2d 

382, 385 (CCPA 1977)). The ensuing sentence states that 

work in preparation for filing related patent applications may suffice (e. g., Rey-Bellet v. Englehardt, 

493 F.2d 1380, 181 USPQ 453 (Cust. & Pat. App. 

1974)), as may work required to develop a first invention in order to develop or reduce to practice a 

second invention (e. g., Keizer v. Bradley, 270 F.2d 

396, 47 CCPA 709, 123 USPQ 215 (1959); Thompson v. Dunn, 166 F.2d 443, 35 CCPA 957, 77 USPQ 

49 (1948)).

Id. The principles underlying the law of diligence have 

long been recognized:

No general standard, by which diligence can be estimated, has been established by the law, nor, in 

the nature of things, is such a standard possible. It 

must be reasonable, under all the circumstances of 

the particular case in question. The character of 

the invention; the health, the means, the liberty of 

the inventor; his occupation upon kindred or subordinate inventions, — are proper subjects for consideration. Such reasonable diligence does not 

involve uninterrupted effort, nor the concentration 

of his entire energies upon this single enterprise.

1 Robinson on Patents § 387, at 548–49 (1890).

The Board criticized ATI for “fail[ing] to provide a reasonable way for us to determine whether unexplained 

lapses have not occurred.” ’053 Op. at 53. Neither LGE

nor the Board raised a question of “unexplained lapses” at 

trial, or requested additional information concerning 
ATI TECHNOLOGIES ULC v. IANCU 21

corroboration. Although the Board also faulted ATI’s 

presentation as “not explain[ing] meaningfully the nature 

of the work” that was being done, ’053 Op. at 51, the Board 

did not inquire of any witness as to the nature of the work. 

In contrast, for example, a Board member asked counsel 

what a “tape out” is, as that usage appeared in the documents. Oral Hr’g. Tr. 76–78. The record does not show 

objection by LGE to the adequacy of the documentation.

The PTAB did not separately explain its ruling of absence of diligence for the ’871 and ’369 patents, where the 

periods were three and six months, respectively. The 

PTAB simply referred to its ’053 patent decision, and 

stated that “Patent Owner relies [on] the same evidence 

and substantially the same arguments in the present review and in IPR2015–00325 in support of its efforts to antedate Lindholm. . . . [I]n IPR2015-00325, the panel 

determined that Patent Owner had not antedated Lindholm. . . . In view of the determination that Patent Owner 

has not antedated Lindholm . . . we conclude that” the challenged claims are unpatentable. ’871 Op. at 3; see ’369 Op. 

at 8–9 (“Patent Owner relies on the same evidence and substantially the same arguments in the instant proceeding 

and in IPR2015-00325, in support of its efforts to antedate 

Lindholm. . . . To the extent necessary, we incorporate here 

the discussion of the antedating of Lindholm from the Final 

Written Decision of IPR2015-00325 by reference.”).

During the ’871 and ’369 patent trials, Mr. Lefebvre

again testified and analyzed the metadata that show diligence from conception to the effective filing date, antedating the Lindholm reference. ’871 patent Lefebvre Decl. 

¶ 41 (J.A. 8001); ’369 patent Lefebvre Decl. ¶ 41 (J.A. 

8443).

Mr. Lefebvre provided an annotated calendar for the 

critical periods. J.A. 8007–34. The calendar summarized 

the various documents that show “the design, development, 

and testing of the R400 sequencer and graphics blocks . . . 
22 ATI TECHNOLOGIES ULC v. IANCU

[which] was necessary to make progress on the sequencer 

block and the shader pipe block.” ’871 patent Lefebvre 

Decl. ¶ 42 (J.A. 8001). The documentation included documents recording metadata on the R400 Sequencer Emulator Folder History, Ex. 2048; Sequencer Parts Development 

Folder History, Ex. 2049; R400 Document Library Folder 

History, Ex. 2050; R400 Architecture Folder History, Ex. 

2051; and R400 GFX Testing Folder History, Ex. 2052. J.A. 

8007.

The PTAB did not provide full analysis for the ’871 and 

’369 patents, and referred to the reasoning in the ’053 opinion. The Board’s rulings as to diligence are in error, in all 

three patents, for the same reasons. These rulings are reversed.

CONCLUSION

The Board erred in holding that diligence had not been 

shown for the three Unified Shader Patents. On the undisputed rulings that conception and constructive reduction to 

practice were shown for the three patents, and on our holding that diligence was shown for the three patents, the 

Board’s decisions of unpatentability of the ’053 patent, the 

’871 patent, and the ’369 patent are reversed.

REVERSED