The term “Synchronous Dynamic Random Access Memory (SDRAM)” refers to a broad category of DRAM modules that rely on the signal sent by the system clock in order to coordinate their functioning with other internal PC components.
SDR SDRAM
A Single Data Rate Synchronous Dynamic Random Access Memory (SDR SDRAM) can read/write one word of data per clock cycle.
SDR SDRAM uses 168 contact pins.
DDR SDRAM
Characteristics of Double Data Rate Synchronous Dynamic Random Access Memory (DDR SDRAM) include:
- 184 contact pins
- Reads/writes 2 words of data per clock cycle
- 1 notch on the module contact surface
| Standard name | DRAM cell array clock (MHz) |
Cycle time (ns) |
I/O bus clock (MHz) |
Data rate (MT/s) |
VDDQ (V) |
Module name | Peak transfer rate (MB/s) |
Timings (CL-tRCD-tRP) |
|---|---|---|---|---|---|---|---|---|
| DDR-200 | 100 | 10 | 100 | 200 | 2.5±0.2 | PC-1600 | 1600 | |
| DDR-266 | 133.33 | 7.5 | 133.33 | 266.67 | PC-2100 | 2133.33 | 2.5-3-3 | |
| DDR-333 | 166.67 | 6 | 166.67 | 333.33 | PC-2700 | 2666.67 | ||
| DDR-400A DDR-400B DDR-400C |
200 | 5 | 200 | 400 | 2.6±0.1 | PC-3200 | 3200 | 2.5-3-3 3-3-3 3-4-4 |
DDR2 SDRAM
Characteristics of Double Data Rate 2 Synchronous Dynamic Random Access Memory (DDR2 SDRAM) include:
- Reads/writes 4 words of data per clock cycle
- 1 notch on the module contact surface
- 240 contact pins
The industry name for DDR2-1066 module is PC2-8500.
The total bandwidth of a DDR2-533 module is 4266 MB/s.
DDR3 SDRAM
Characteristics of Double Data Rate 3 Synchronous Dynamic Random Access Memory (DDR3 SDRAM) include:
- Reads/writes 8 words of data per clock cycle
- 1 notch on the module contact surface
- 240 contact pins
The industry name for DDR3-1333 module is PC3-10600.
The total bandwidth of a DDR3-1600 module is 12800 MB/s.