MIPS Technology Inc has filed a patent infringement case against rival core developer Lexra Inc. The suit, filed by MIPS Technologies in the US District Court for the Northern District of California, alleges that Waltham, Massachusetts-based Lexra has infringed two patents that cover fundamental aspects of the MIPS RISC architecture.

MIPS says that it has brought the case to protect its intellectual property. We’re an intellectual property company, that’s a primary asset, said Brain Knowles, VP of worldwide marketing at MIPS. The company has tempestuous legal history with Lexra, last year MIPS sued it over claims of MIPS compatibility.

The patents relate to a method of reading and writing data less than a word long and also speeding up extended precision arithmetic operations. MIPS says Lexra’s LX 4080, LX 4080P, LX 4180, LX 4280 and LX 5280 cores infringe US. Patent no. 4,814,976 and that the LX 4280 and LX 5280 infringe US Patent no 5,864,703. Lexra has 20 days to reply to the allegations.