Return jump stack
Indirect jumps difficult to predict except returns from procedures
If returns are entered with their target address in BTB, most of the time it will be the wrong target
Hence addition of a small “return stack”; 4 to 8 entries are enough (1 in MIPS R10000, 4 in Alpha 21064, 4 in Sparc64, 12 in Alpha 21164)
None needed in ISA’s that have a special link register (e.g., Power PC)