Clean room design

Clean-room design (also known as the Chinese wall technique) is the method of copying a design by reverse engineering and then recreating it without infringing any of the copyrights associated with the original design. Clean-room design is useful as a defense against copyright infringement because it relies on independent creation. However, because independent invention is not a defense against patents, clean-room designs typically cannot be used to circumvent patent restrictions. The term implies that the design team works in an environment that is "clean" or demonstrably uncontaminated by any knowledge of the proprietary techniques used by the competitor. Typically, a clean-room design is done by having someone examine the system to be reimplemented and having this person write a specification. This specification is then reviewed by a lawyer to ensure that no copyrighted material is included. The specification is then implemented by a team with no connection to the original examiners. Phoenix Technologies sold its clean-room implementation of the IBM-compatible BIOS to various PC clone manufacturers. Several other PC clone companies, including Corona Data Systems, Eagle Computer, and Handwell Corporation, were litigated by IBM for copyright infringement, and were forced to re-implement their BIOS in a way which did not infringe IBM's copyrights. The legal precedent for firmware being protected by copyright, however, hadn't been established until Apple Computer, Inc. v. Franklin Computer Corp., 714 F.2d 1240 (3rd Circuit Court 1983). The three settlements by IBM, and the legal clean-room PC BIOS designs of Compaq and Columbia Data Products, happened before Phoenix announced, in July 1984, that they were licensing their own BIOS code. Phoenix expressly emphasized the clean-room process through which their BIOS code had been written by a programmer who did not even have prior exposure to Intel microprocessors, himself having been a TMS9900 programmer beforehand.