What methods do processors use to communicate with each other?

Processors can interact with each other in several ways, depending on the architecture and system:

• Shared Memory: multiple processors access a common memory area, exchanging data through it. Synchronization mechanisms such as locks, semaphores, or atomic operations are used.

• Message Passing: processors exchange messages via special channels or buses. This can be implemented through hardware means (e.g., inter-processor buses) or software protocols.

• Cache Coherency: in multi-processor systems with shared memory, cache coherence is maintained so that changes in one processor are visible to others.

• Inter-Processor Interrupts (IPI): processors can send interrupts to each other for synchronization or notification.

• Specialized Buses and Interfaces: for example, multi-processor systems use buses like QuickPath Interconnect (QPI) or HyperTransport for data exchange.

Thus, the choice of method depends on the system architecture and requirements for performance and synchronization.