Emerging Technologies of Computation

1. Emerging Technologies of Computation Montek Singh COMP790-084 Oct 11, 2011

2. Today: Multicore Systems • Basics of multicore systems • what is multicore? • why multicore? • main features • examples • Next two classes • case studies • benefits and challenges • key research problems

3. What is Multicore Design? • Two or more CPU cores on a single die • typically share L2 cache • typically separate L1 caches • share main memory

4. Why Multicore? • What was happening before c. 2010? • What started happening c. 2010? • Why?

5. Why Multicore? • Three main technological reasons • Memory Wall • increasing gap between CPU and memory speeds • no longer makes sense to simply make CPU faster • ILP Wall • increasing difficulty in finding enough parallelism in single stream of instructions • tried hyper-threading already • Power Wall • increasing frequency was increasing power density without so much increase in performance • poses big manufacturing problems

6. Why Multicore?

7. Why Multicore? • Main manufacturing advantages over discrete processors • on-chip caches faster • shared L2 cache • physical proximity of CPUs allows cache coherence circuitry to be much faster • inter CPU communication much faster than traditional multiprocessor supercomputers • much less PCB area than discrete processors • higher performance/power ratio • voltage scaling

8. Let’s talk buses • Frontside and Backside buses • Northbridge and Southbridge

9. Example: Intel i7

10. Example: ARM Cortex-A9

11. Example: NVIDIA