> Now, to support multiple processors on a single machine reading and writing from the same memory in a coherent way, only one processor on a machine can have exclusive access to a given cache line.
Does this also apply when multiple processors are only reading memory?
No. That's what MESI-based cache protocols are all about. Multiple cores/processors can have the same cache line in a shared/read-only state. Only writes require exclusive access.
Does this also apply when multiple processors are only reading memory?