Alpex Computer Corp. v. Nintendo Co.
102 F.3d 1214 (Fed. Cir. 1996)

I. Background

In the mid-1970’s, Alpex Computer Corporation developed and patented a new home video game system technology using removable, ROM-based cartridges, which was later commercialized by Atari, Mattel, and Coleco. Nintendo entered the video game system market in the early 1980’s with its popular Nintendo Entertainment System (NES). In February 1986, Alpex filed a lawsuit against Nintendo, alleging infringement of one of its video game system patents, U.S. Patent No. 4,026,555, relating to its video display system.

The ‘555 patent developed a process for generating video signals using RAM, controlled by a microprocessor, where the RAM contained a storage position corresponding to each pixel on the television screen, totaling approximately 32,000 pixels. As the cathode ray beam in the television scanned across each pixel on the screen, display data would be provided from the corresponding position in RAM. This video display system, referred to as “bit-mapping,” provided greater control and more flexibility than prior systems. Claims 12 and 13 of the ‘555 patent are reproduced below:

12. Apparatus for playing games by displaying and manipulating player and ball image devices on the screen of a display tube, comprising:
first means for generating a video signal representing a linear player image device aligned in a first direction,
second means for generating a video signal representing a ball image device,
manually operable game control means, and
means responsive to said manually operable game control means for causing said first means to generate a video signal representing the player image device rotated so that it is aligned in a second direction different from said first direction.

13. Apparatus according to claim 12, wherein said means for causing includes programmed microprocessor means and a replaceable memory having program game instructions stored therein for controlling said microprocessor means, whereby different games may be played with said apparatus by replacing said replaceable memory.

The NES video display system used what Nintendo called an “on-the-fly” technique. Instead of storing the display data for the entire screen in RAM, Nintendo’s system used eight shift registers, controlled by a picture processing unit (PPU), to alter a portion of the screen, up to 64 pixels, at a time. The NES PPU technology was faster and smoother than Alpex’s bit-mapping technology.


Alpex was successful at trial, where the jury determined that Nintendo’s technology infringed Alpex’s ‘555 patent and awarded Alpex damages totaling $253,641,445. The district court denied Nintendo’s post-trial motions and upheld the verdict. Nintendo appealed.

II. Issue

The primary issue before the Federal Circuit centered on the proper claim construction of two claims, claims 12 and 13, specifically focusing on the language “means for generating a video signal,” and whether those claims included the NES video display technology.

III. Analysis

A. Trial Court

Pursuant to 35 U.S.C. § 112 ¶ 6, the trial court interpreted “means for generating a video signal” based on the structure defined in the ‘555 patent specification and drawings. Specifically, the jury was instructed that claims 12 and 13 corresponded to the structure in Figure 2 of the ‘555 patent, which consisted of ROM memory, a microprocessor, display RAM, display RAM control, and a television interface.

Nintendo argued that the trial judge approved an erroneous claim construction. Nintendo reasoned that its use of shifting registers for changing up to 64 pixels at a time was different from Alpex’s use of a RAM-based, bit-mapping system for changing one or all of the 32,000 pixels on a screen at a time. Nintendo also argued that Alpex was barred from claiming that Nintendo’s technology infringes on the ‘555 patent, because during prosecution, Alpex distinguished its technology from a prior art patent using shifting registers. Alpex argued that Nintendo waived its right to use prosecution history for prosecution history estoppel purposes.

A. Federal Circuit

1. Literal Infringement

The Federal Circuit first recognized that claims 12 and 13 were means-plus-function claims, and thus § 112 ¶ 6 required interpreting those claims “in view of the structure disclosed in the specification of the patent.” The court held, however, that “positions taken before the PTO may bar an inconsistent position on claim construction under § 112 [¶ 6.]” Therefore, Alpex’s claims cannot be construed to cover a technology that has the same functional and structural traits as a prior art patent that Alpex admitted was not covered by its claims during prosecution. By allowing such a construction, the court concluded that the district court erred in sustaining the jury verdict of literal infringement.

2. Doctrine of Equivalents

The Federal Circuit then established that “equivalency under the doctrine of equivalents and equivalency under § 112 ¶ 6 . . . each has a separate origin, purpose, and application.” Under § 112, the concern is whether the structures of the claimed device and the accused device are equivalent, whereas under the doctrine of equivalents the concern is whether the devices are only “insubstantially different.” The court concluded that because Alpex’s expert made only conclusory statements regarding the substantial similarity in terms of function/way/result, the evidence “does not support a finding of infringement under the doctrine of equivalents.” Further, the court expressed that the purpose of the doctrine of equivalents is to “prevent others from avoiding the patent by merely making ‘unimportant and insubstantial changes and substitutions in the patent,’” and held that Nintendo’s use of shift registers instead of RAM was not “merely an unimportant and insubstantial change.”

Thus, the Federal Circuit reversed the district court’s judgment as to infringement and damages.

Thanks to Brandon Rash for his assistance in the preparation of this case summary.