Graphics chip designer Intergraph filed a lawsuit against Intel. Monday, claiming that Intel's 64-bit Itanium chip architecture violates two Intergraph patents, Intergraph said in a statement. The patents relate to parallel instruction computing (PIC), which helps speed up the operation of processors. Intergraph said Intel's EPIC (explicitly parallel instruction computing) architecture violates patents that Intergraph holds on PIC. Intergraph developed PIC in 1992 for its C5 Clipper graphics chip, and filed for patents in 1993, the company said in a statement. The two patents cover: -- the techniques used to convey compiler-recognized parallelism to the hardware; -- a novel approach to routing instructions to any of the processing units. The two patents are key to the performance of Itanium chips, Intergraph said in the statement Intergraph and Intel have a four-year history of litigation. The companies worked together between 1993 and 1996 on advanced chip design, but in 1996 Intergraph claimed that Intel began making unreasonable demands for royalty-free rights to Intergraph patents already being used in Intel microprocessors. Intergraph filed suit in 1997 claiming coercive behavior, patent infringement, and antitrust violation on Intel's part. The antitrust portion of that suit was dismissed last month but the patent infringement case involving Intel's Pentium family of processors continues. This new lawsuit is completely separate, Intergraph said in its statement.