The HYS72Dxx5x0GR are low profile versions of the standard Registered DIMM modules with 1.2" inch (30,40 mm) height for 1U Server Applications. The Low Profile DIMM versions are available as 32M x 72 (256MB), 64M x 72 (512MB) and 128M x 72 (1 GB). The memory array is designed with Double Data Rate Synchronous DRAMs for ECC applications. All control and address signals are re-driven on the DIMM using register devices and a PLL for the clock distribution. This reduces capacitive loading to the system bus, but adds one cycle to the SDRAM timing. A variety of decoupling capacitors are mounted on the PC board. The DIMMs feature serial presence detect based on a serial E2PROM device using the 2-pin I2C protocol. The first 128 bytes are programmed with configuration data and the second 128 bytes are available to the customer.