1. Coherency Hub Design for Multi-socket Sun Servers with CoolThreads (TM) Technology
- Author
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Stephen E. Phillips, John R. Feehrer, Paul Gingras, P. Rotker, Milton Shih, Peter Yakutis, and John R. Heath
- Subjects
UltraSPARC ,Transaction processing ,Computer science ,Multiprocessing ,02 engineering and technology ,computer.software_genre ,Pipeline (software) ,020202 computer hardware & architecture ,UltraSPARC T2 ,Hardware and Architecture ,Server ,Scalability ,0202 electrical engineering, electronic engineering, information engineering ,Operating system ,Electrical and Electronic Engineering ,computer ,Database transaction ,Software - Abstract
This paper describes the micro-architecture of a Coherency Hub (CoHub) ASIC for a 4-socket highly-threaded multiprocessor using Sun's UltraSPARC ¯ T2 Plus processor. UltraSPARC T2 Plus is an 8-core CMT processor in the Sun Servers with CoolThreadsTM Technology family. CoHub enables cost-effective scaling to 4 nodes with a total thread count of 256 and near-linear performance scaling on transaction processing workloads. Extending a 2-node "glueless" system to a 4-node system without processor changes was a key requirement. CoHub broadcasts snoop requests, serializes requests to the same address, and consolidates snoop responses. It communicates with nodes via serial links, using a proprietary link layer implemented over FBDIMM. We present the coherency scheme, ASIC design, transaction flows, and engineering challenges created by 800 MHz operation and 6-stage pipeline budget. We report performance scalability results measured on commercial server benchmarks.
- Published
- 2017
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