19. TerminologyΒΆ

Program Counter (PC)
A weird, terrible, anachronistic term to describe the address in memory of an instruction.
Fetch Packet
A bundle returned by the front-end which contains some set of consecutive instructions with a mask denoting which instructions are valid, amongst other meta-data related to instruction fetch and branch prediction. The Fetch PC will point to the first valid instruction in the Fetch Packet, as it is the PC used by the Front End to fetch the Fetch Packet.
Fetch PC
The PC corresponding to the head of a Fetch Packet instruction group.
Out-of-Order (OOO)
Refers to the microarchitecture of a core in which instructions are re-ordered according to their dependencies.