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#pipeline
2 posts
RISC-VRISC-V Branches and Jumps: Resolve Stage, JAL/JALR, Return-Address Stack Hints
Part 18 of the RISC-V series. I added the branch resolve stage, JAL redirect in ID, BTFN static prediction, and a RAS that follows the hints in spec section 2.5 to a pipeline model and compared them. CPI dropped from 1.368 to 1.227, and an 8-entry RAS predicted 98.3% of fib's returns.
RISC-VRISC-V 5-Stage Pipeline: Forwarding and Stall Conditions, Handling x0
Part 17 of the RISC-V series. I ran the same programs on a 5-stage pipeline model, matched them against QEMU, and measured CPI: 1.37 with forwarding, 1.83 without. Dropping the rd≠0 condition made a program using the HINT ntl.all write 0x80000000 instead of 0.