12GB Total memory using 3pc of 4GB 1333MHz Module 240pin dimm DDR3 10600. Genuine CMS brand, CMS is one of the most trusted names in the Computer Memory industry and this product carries a Lifetime Warranty from CMS Expansion: 6 Sockets (2 banka of 3) Maximun Memory: 24 GB with 64-bit OS Compatible with Dell Studio XPS 9100 MODULES MUST BE ORDERED AND INSTALLED IN GROUPS OF THREE for Triple Channel Mode. System also supports Dual Channel Mode when installing in pairs. If 4GB is installed, the recognized memory may be reduced to 3.5GB or less (depending on system configuration and memory allocation). Maximum configurations require a 64-bit operating system.