HP ProLiant SL165s Memory technology evolution: an overview of system memory t - Page 15

industry based the DDR-SDRAM naming convention on the actual peak data transfer rate in MB/s. For example, PC266 is equivalent to PC2100 (64 bit * 2 * 133 MHz = 2.1 GB/s or 2100 MB/s). DDR3 SDRAM DIMM manufacturers produce two types of DIMMs: Unbuffered DIMMs (UDIMM) and Registered DIMMs (RDIMM). UDIMMs are the most basic type of memory module and offer a lower latency and low power consumption but are limited in capacity. An E suffix in the manufacturer's module name identifies Unbuffered DIMMs with ECC. RDIMMs offer larger capacities than UDIMMs and include address parity protection. An R suffix in the module manufacturer's name identifies Registered DIMMs. Table 2. Summary of DDR SDRAM technologies Type DDR1 DDR2 DDR3 Component naming convention DDR200 DDR266 DDR333 DDR400 DDR2-400 DDR2-533 DDR2-667 DDR2-800 DDR3-800 DDR3-1066 DDR3-1333 DDR3-1600 Module naming convention PC1600 PC2100 PC2700 PC3200 PC2-3200R PC2-4300 PC2-5300 PC2-6400 PC3-6400 PC3-8500 PC3-10600 PC3-12800 Bus speed 100 MHz 133 MHz 166 MHz 200 MHz 200 MHz 266 MHz 333 MHz 400 MHz 400 MHz 533 MHz 667 MHz 800 MHz Peak bandwidth 1.6 GB/s 2.1 GB/s 2.7 GB/s 3.2 GB/s 3.2 GB/s 4.3 GB/s 5.3 GB/s 6.4 GB/s 6.4 GB/s 8.5 GB/s 10.6 GB/s 12.8 GB/s Fully-buffered DIMMs Traditional DIMM architectures use a stub-bus topology with parallel branches (stubs) that connect to a shared memory bus (Figure 11). Each DIMM connects to the data bus using a set of pin connectors. For the electrical signals from the memory controller to reach the DIMM bus-pin connections at the same time, all the traces must be the same length. This can result in circuitous traces on the motherboard between the memory controller and memory slots. Both the latency resulting from complex routing of traces and signal degradation at the bus-pin connections cause the error rate to increase as the bus speed increases. 15