08-Lecture - 1 The College of Computing Georgia Institute...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 The College of Computing Georgia Institute of Technology 1 CS 4290/6290 – Lecture 08 – Case Studies CS 4290/6290 – Lecture 08 Case Studies (Lectures based on the work of Jay Brockman, Sharon Hu, Randy Katz, Peter Kogge, Bill Leahy, Ken MacKenzie, Richard Murphy, Michael Niemier, and Milos Pruvlovic) 2 The College of Computing Georgia Institute of Technology 2 CS 4290/6290 – Lecture 08 – Case Studies Speculation: The Picture 3 The College of Computing Georgia Institute of Technology 3 CS 4290/6290 – Lecture 08 – Case Studies ROB vs. Register Renaming • How many ports do we need for the ROB? • Lots! Look at a single-issue processor: – Issue: read two entries and write one – Write Result: write one entry – Commit: read and write one entry • ROB has a dual role – Keeps results (names) – Keeps order • Let’s split the two roles 4 The College of Computing Georgia Institute of Technology 4 CS 4290/6290 – Lecture 08 – Case Studies ROB vs. Register Renaming • Keeping results: physical registers – Have a large physical register file – Keep architected-to-physical mapping in a table – Physical registers hold all values (names) • Keeping order: simplified ROB – Only keeps info needed to commit instructions • Reservation stations also simplified – No need to keep values – Called “instruction window” instead of RS 5 The College of Computing Georgia Institute of Technology 5 CS 4290/6290 – Lecture 08 – Case Studies How does it work? • Rename – Find in the rename RAT (Register Allocation Table) which physical registers are sources – Get a free physical register for destination and change rename RAT • Dispatch – Wait in window until all source registers have values, then – Read source values from registers • Write Result – Send result to destination register – Send destination register number to window 6 The College of Computing Georgia Institute of Technology 6 CS 4290/6290 – Lecture 08 – Case Studies Committing • Wait until oldest instruction done • Change commit RAT – Before it said Rn is in Pj – Now change it so Rn is in Pk (the destination) • Free physical register Pj – Everything that wants Pj is already committed – All future uses of Rn should use Pk 7 The College of Computing Georgia Institute of Technology 7 CS 4290/6290 – Lecture 08 – Case Studies Recovering Precise State • To get precise state after instruction X, we – Wait until X commits – The commit RAT is the precise state • E.g. recovery from branch misprediction – Wait until X commits – Rename map = commit map – Flush window & ROB, restart fetch 8 The College of Computing Georgia Institute of Technology 8 CS 4290/6290 – Lecture 08 – Case Studies Reading Assignment • J. E. Smith and A. R. Pleszkun, “Implementing Precise Interrupts in Pipelined Processors", IEEE Transactions on Computers, 37(5), pages 562-573, May, 1988....
View Full Document

This note was uploaded on 11/16/2011 for the course SCIENCE Anatomy an taught by Professor Tory during the Spring '11 term at Kennesaw.

Page1 / 59

08-Lecture - 1 The College of Computing Georgia Institute...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online