Lexra was a semiconductor intellectual property core company based in Waltham, Massachusetts. It was founded in 1997 and began developing and licensing semiconductor intellectual property cores that implemented the MIPS-I instruction set, except for the four unaligned load and store (lwl, lwr, swl, swr) instructions.
Lexra did not implement those instructions because they are not necessary for good performance in modern software and Silicon Graphics owned a patent that had originally been granted to MIPS Computer Systems Inc. for implementing unaligned loads and stores in a RISC processor and Lexra did not wish to pay a high license fee for permission to use the patent.
Lexra licensed soft cores unlike ARM Ltd at the time. Lexra was probably the first semiconductor intellectual property core company to do so.
In 1998 Silicon Graphics spun out MIPS Technologies Inc. as a semiconductor IP licensing company that would compete directly with Lexra. MIPS Technologies sued Lexra claiming a trademark infringement for Lexra's claims of compatibility with the MIPS-I instruction set. Lexra and MIPS Technologies settled the dispute by agreeing that in all public statements Lexra would clearly state that it did not implement unaligned loads and stores.
In 1999 MIPS Technologies sued Lexra again, but this time for infringing its patents on unaligned loads and stores. Though Lexra's processor designs did not implement unaligned loads and stores, it was possible to emulate the functionality of unaligned loads and stores through a long series of other instructions. In the opinion of Lexra, the ability to emulate the function of unaligned loads and stores in software predated the grant of the patent in question and could not be viewed as an infringement of the hardware patent by any reasonable interpretation. Also, much earlier than any MIPS Technologies processor, IBM mainframes supported unaligned memory operations. In these earlier IBM processors, unaligned memory operations and partial access to registers were available through microcode and the instruction set architecture. These aspects of earlier IBM processors posed the much greater threat of patent invalidation to MIPS Technologies, compared to the seemingly vacuous MIPS Technologies infringement claim against Lexra.
The protracted second lawsuit combined with a downturn in semiconductor industry business forced Lexra into a settlement with MIPS Technologies that included MIPS Technologies paying Lexra a large sum of money and granting Lexra a license to its technologies in exchange for Lexra exiting the IP business.
Lexra failed as a networking / communications fabless semiconductor chip company and ceased operations in January 2003.
In its 5.5 years, Lexra implemented ten processor designs and licensed nine of them as IP cores. Lexra had the first
- Synthesizable (RTL to gates) MIPS processor core allowing customer owned tools and customer chosen foundry.
- IP core to support EJTAG on-chip debug;
- IP core to support MIPS16 code compression;
- RISC processor IP core with a 6-stage pipeline; and later the first with a 7-stage pipeline;
- dual-issue superscalar processor IP core;
- coarse-grained multithreaded processor IP core and later the first fine-grained multithreaded processor IP core
Lexra also enhanced the MIPS-I instruction set with extensions that greatly enhanced performance for digital signal processing (DSP) algorithms.
- The Lexra Story by former employee Jonah Probell