This specification defines the electrical and mechanical requirements for 240-pin, PC2-4200/PC2-5300/PC2-6400, 72 bit-wide, Fully Buffered Double Data Rate Synchronous DRAM Dual In-Line Memory Modules (DDR2 SDRAM FB-DIMMs).These SDRAM FB-DIMMs are intended for use as main memory when installed in systems such as servers and workstations. PC2-4200/PC2-5300/PC2-6400 refers to the DIMM naming convention in which PC2-4200/PC2-5300/PC2-6400 indicates a 240-pin DDR2 DIMM running at 266/333/400 MHz DRAM clock speed and offering 4266/5333/6400 MB/s bandwidth.