The SPEC XPC is the X Performance Characterization project, working, under the SPEC GPC group. It develops new graphical benchmark methods and performance reporting procedures, that have value to both the user and vendor communities.
In 1993, the XPC project group developed Xmark93, a standardized benchmarking tool for measuring the performance of computer systems running the X Window System.
References
SPEC XPC Wikipedia(Text) CC BY-SA