| Type of Memory | Description |
| DRAM (Dynamic RAM) | Memory that must be refreshed. |
| SRAM (Static RAM) (L1, L2, L3) | Does not require refresh. Used for cache memory. |
| SDRAM (Synchronous Dynamic RAM) | Synced with the CPU clock. 168-pin. |
| DDR (Double Data Rate) SDRAM | Data read on rising and falling edge of computer clock to double the bandwidth of SDRAM. 184-pin, 64-bit DIMM. |
| DDR2 | Similar to DDR but 240-pin, 64-bit DIMM. Faster than DDR. |
| Single Ranked DDR | Uses one DDR module in a single slot. |
| Double Ranked DDR | Uses two DDR modules in two slots to double bandwidth to the system bus. |
Form Factors
| Form Factor | Description |
| DIMM (Dual Inline Memory Module) | 168, 184, or 240-pin. Pins on both sides are independent. SDRAM uses DIMM. 64-bits. |
| SoDIMM (Small outline DIMM) | Used in notebook computers. 72-pin is 32-bits and 144-pin is 64-bits. |
| MicroDIMM | Smaller than a SoDiMM, used in sub-notebook computers. 144-pin SDRAM, 172-pin DDR, 214-pin DDR2. |
| RIMM (Rambus Inline Memory Module) | 184 or 168-pin, 16 or 32-bit, 800-1600 MHz, 2 notches. Each RIMM slot must be filled. C-RIMM can fill empty slots. Uses heat spreader. Current DDR and DDR2 is faster and less expensive. |
Calculating DDR Memory performance:
MHz x Clock Cycles x Bus Width
Example:
500 MHz x 2 clock cycles x 8 bytes = 8,000
500 x 2 x 8 = 8,000
This memory would have a throughput value of 8,000 MB per second (or 8 GB per second) and would be referred to as PC2-8000