Department of Electrical Engineering and Computer Science

Coherence Ordering For Ring-Based Chip Multiprocessors

Michael R. Marty and Mark D. HillUniversity of Wisconsin—Madison

[LINK]

Department of Electrical Engineering and Computer Science

Overview• Rings a viable interconnect for future CMPs.

• Cache Coherence in rings:• Ordering Point• Greedy Order

• Ring-Order:• Improves performance relative to ordering point by activating

requests immediately.• Improves performance stability relative to greedy order by

not using retries.

Department of Electrical Engineering and Computer Science

ORDERING-POINT

Department of Electrical Engineering and Computer Science

GREEDY-ORDER

Department of Electrical Engineering and Computer Science

RING-ORDER

Department of Electrical Engineering and Computer Science

THIS IS HOW CMP WITH RING LOOKS!

Department of Electrical Engineering and Computer Science

EVALUATION SYSTEM

Department of Electrical Engineering and Computer Science

RESULT: RUNTIME

Department of Electrical Engineering and Computer Science

RESULT: L2 MISSES & RING TRAFFIC

Department of Electrical Engineering and Computer Science

RESULT: MISS LATENCIES & REQUEST

Department of Electrical Engineering and Computer Science

STATE TRANSITION

Department of Electrical Engineering and Computer Science

Questions?

Department of Electrical Engineering and Computer Science

Thank You

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