Abstract: A new memory subsystem called Memory Expansion Technology (MXT)has been built for compressing main memory contents. MXT effectively doubles the physically available memory. This paper provides an analysis of the performance impact of memory compression using the SPEC2000 benchmarks and a database benchmark. Results show that the hardware compression of memory has a negligible performance penalty compared to a standard memory. We also show that many applications? memory contents can be compressed usually by a factor of two to one. We demonstrate this using industry benchmarks, web server benchmarks, and contents of popular web sites.