The HYS 72Dxx0x0GR are industry standard 184-pin 8-byte Dual in-line Memory Modules (DIMMs) organized as 32M x 72 (256MB), 64M x 72 (512MB) and 128M x 72 (1GB). 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.