The HB54A5129F1U is a 64M x 72 x 1 bank Double Data Rate (DDR) SDRAM Module, mounted 18 pieces of 256Mbits DDR SDRAM (HM5425401BTT) sealed in TSOP package, 1 piece of PLL clock driver, 2 pieces of register driver and 1 piece of serial EEPROM (2k bits EEPROM) for Presence Detect (PD). Read and write operations are performed at the cross points of the CK and the /CK. This high-speed data transfer is realized by the 2-bit prefetch-pipelined architecture. Data strobe (DQS) both for read and write are available for high speed and reliable data bus design. By setting extended mode register, the on-chip Delay Locked Loop (DLL) can be set enable or disable. An outline of the products is 184-pin socket type package (dual lead out). Therefore, it makes high density mounting possible without surface mount technology. It provides common data inputs and outputs. Decoupling