Memory technology evolution: an overview of system memory technologies, 9th edition

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 Component

naming

convention

Module naming

convention

Bus speed Peak bandwidth

DDR1 DDR200 PC1600 100 MHz 1.6 GB/s

DDR266 PC2100 133 MHz 2.1 GB/s

DDR333 PC2700 166 MHz 2.7 GB/s

DDR400 PC3200 200 MHz 3.2 GB/s

DDR2 DDR2-400 PC2-3200R 200 MHz 3.2 GB/s

DDR2-533 PC2-4300 266 MHz 4.3 GB/s

DDR2-667 PC2-5300 333 MHz 5.3 GB/s

DDR2-800 PC2-6400 400 MHz 6.4 GB/s

DDR3 DDR3-800 PC3-6400 400 MHz 6.4 GB/s

DDR3-1066 PC3-8500 533 MHz 8.5 GB/s

DDR3-1333 PC3-10600 667 MHz 10.6 GB/s

DDR3-1600 PC3-12800 800 MHz 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.