Indeed you can take this further and think of three address spaces:
- Visible register file. 4-6 bit address space, up to 2kb in size. Virtualized as hidden (hardware) registers. Single cycle access. Usually little or no access controls or fault handling, if it exists you can read/write it.
- Main memory, 32-64 bit address space. Virtualized as caches, main RAM and swap. Access may be as low as 5 cycles for L1d, hundreds for main RAM, up into millions if you hit the swap file. Straightforward layer of access controls: memory protection, segfault exceptions and so on.
- Far storage, URIs and so on. Variable-length address space, effectively infinite. Arbitrarily long access times, arbitrarily complex access controls and fallbacks.
Comments
Indeed you can take this further and think of three address spaces:
- Visible register file. 4-6 bit address space, up to 2kb in size. Virtualized as hidden (hardware) registers. Single cycle access. Usually little or no access controls or fault handling, if it exists you can read/write it.
- Main memory, 32-64 bit address space. Virtualized as caches, main RAM and swap. Access may be as low as 5 cycles for L1d, hundreds for main RAM, up into millions if you hit the swap file. Straightforward layer of access controls: memory protection, segfault exceptions and so on.
- Far storage, URIs and so on. Variable-length address space, effectively infinite. Arbitrarily long access times, arbitrarily complex access controls and fallbacks.