512MB PC2-6400 NP DDR2 SDRAM UDIMM Help improve the overall performance of your ThinkCentre systems with the 512MB PC2-6400 Non-Parity (NP) DDR2 SDRAM Unbuffered DIMM (UDIMM) memory upgrade. PC2-6400 DDR2 SDRAM enables up to six times the performance of traditional SDRAM. Adding additional ThinkCentre memory is a cost-effective way to help boost your system performance and enhance your ability to run more programs simultaneously.