Alpex Computer Corp. v. Nintendo Co., Ltd.

The ’555 patent was issued to Alpex Computer Corporation (plaintiff) for the invention of a microprocessor-based gaming console that read unique game cartridges to allow users to play a variety of more complex games. The patent claimed a keyboard-controlled apparatus for producing video signals through random access memory (RAM) with storage positions corresponding to each unique position of a television raster. A raster was composed of around 32,000 dots or bars that a cathode-ray beam illuminated on a regular cycle to create images on the screen. The patented invention used RAM to hold a bit of data for each of the thousands of memory positions needed to represent the map of the raster image. The display system was called bit-mapping. Using RAM for bit-mapping allowed consoles to create more complex images on screen but slowed down the system operations. While prosecuting its patent application, Alpex distinguished its RAM-based bit-mapping display structure from the structure of a prior art patent called Okuda. Okuda utilized a shift register-based display structure. The structure placed pre-formed horizontal slices of data within eight shift registers—digital circuits used for data storage—and processed the slices directly to a screen. The process repeated as necessary to change images. The shift-register display operated faster than bit-mapping by processing slices of images as opposed to entire screens, and Alpex specifically argued to differentiate the systems during prosecution. Nintendo Co., Ltd. (defendant) produced the Nintendo Entertainment System (NES), a game console that used a picture-processing unit (PPU) to process images as part of a shift-register-display structure. Alpex sued Nintendo for patent infringement, and the jury ruled in favor of Alpex, awarding damages. Nintendo moved for judgment as a matter of law at to the infringement or for a new trial. The court denied Nintendo’s motions. Nintendo appealed, and Alpex cross-appealed the amount of damages. Nintendo argued that the differences between the two image-display systems and the patent prosecution history disproved any infringement claims and also asserted the doctrine of prosecution-history estoppel as an infringement defense.