Semiconductor Memory
SRAM, DRAM, ROM, EEPROM and Flash — how chips store data.
Easy
| Type | Volatile | Notes |
|---|---|---|
| SRAM | yes | 6 transistors per bit; fast; CPU caches and MCU RAM |
| DRAM | yes | 1 transistor + 1 capacitor; must be refreshed; PC main memory |
| Mask ROM | no | fixed at manufacture |
| EEPROM | no | byte-erasable; ~100k–1M write cycles; settings storage |
| NOR Flash | no | random read access; execute-in-place firmware |
| NAND Flash | no | dense, block access; SSDs, SD cards, USB drives |
Flash must be erased in blocks before writing and wears out, so wear levelling spreads writes across blocks.
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