Memory access speeds
| Level |
Memory Type |
Typical Access Time |
Size Range |
| Registers |
CPU Registers |
10^0 ns |
A few KB (typically) |
| L1 Cache (Level 1) |
On-chip Cache |
10^0 to 10^1 ns |
32 KB to 128 KB |
| L2 Cache (Level 2) |
On-chip Cache |
10^1 ns |
256 KB to 4 MB |
| L3 Cache (Level 3) |
On-chip/Shared Cache |
10^1 to 10^2 ns |
4 MB to 32 MB |
| Main Memory (DRAM) |
RAM |
10^2 ns |
4 GB to 128 GB (more) |
| Non-volatile Memory |
SSD (Flash memory) |
10^4 to 10^5 ns |
128 GB to 4+ TB |
| Secondary Storage |
HDD |
10^6 to 10^7 ns |
1 TB to 12+ TB |
| Tertiary Storage |
Cloud/Network Storage |
10^7 to 10^8 ns |
Virtually unlimited |
References
- What Every Programmer Should Know About Memory (html | pdf)
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