The central processing unit (CPU) is the main processor in a computer. It executes the instructions of programs, and often is the primary control unit in a computer.
CPUs aren’t good for heavy or parallel arithmetic. What this means is that specialised hardware (like GPUs) are necessary for some tasks.
Privilege modes
Most CPU architectures contain specific privilege modes, which allow programs to use more or less types of instructions. In order of most privilege to least privilege:
- M-mode (machine) — where bootloader software and firmware operate
- H-mode (hypervisor) — where virtual machines operate
- S-mode (supervisor) — where the kernel operates
- U-mode (user) — where applications and software libraries operate
Some architectures may omit certain levels of this by default, or add additional levels. For example, Nios II by default only has U and S-modes. RISC-V supports M, S, and U-modes, with an additional extension for H-mode.
Sub-pages
- IP core
- Components and modules