Computer memory stores information, such as data and programs, for immediate use in the computer. The term memory is often synonymous with the terms RAM, main memory, or primary storage.
Modern computer memory is implemented as semiconductor memory, where data is stored within memory cells built from MOS transistors and other components on an integrated circuit. There are two main kinds of semiconductor memory: volatile and non-volatile
Volatile memories include:
- Registers: Temporary storage for data being processed by the CPU.
- SRAM (Static Random-Access Memory): Used for CPU cache.
- DRAM (Dynamic Random-Access Memory): Main system memory.
Non-volatile memories include:
- NVM (Non-Volatile Memory) / SCM (Storage Class Memory): Bridges the gap between DRAM and SSDs.
- SSD (Solid-State Drive): Long-term data storage.
- HDD (Hard Disk Drive): Long-term data storage.
| Technology | Latency | Price ($/GB) |
|---|---|---|
| Register | 0.1-1 ns | N/A |
| SRAM | 1-10 ns | $1000-5000 |
| DRAM | 10-100 ns | $5-10 |
| NVM/SCM | 100-1000 ns | $20-50 |
| SSD (NVMe) | 10-100 μs | $0.10-0.30 |
| HDD | 1-10 ms | $0.02-0.05 |
See also: von Neumann Architecture Memory Address