Cores, Cache, Content, and Characterization: IBM’s Second Generation 14-nm Product, z15

摘要

The IBM z15 system improves upon the prior-generation z14 design within the same chip footprint and technology node, while featuring the addition of two cores, 33%/100%/43% additional L2/L3/L4 cache, as well as additional core features and on-chip accelerators. The largest 5-drawer system configuration includes 20 central processor (CP) chips, five system controller (SC) chips, and 40 TB of memory. With similar to 200 cores across all CP chips operating with 99.99999% uptime at 5.2 GHz, z15 achieves a 25% increase in system capacity and a 14% single thread performance improvement over the z14 system. In this article, we describe the key design factors and system/characterization refinement that enabled these results, including the novel 2-Mb embedded dynamic random access memory (eDRAM) cell, a new voltage droop monitor, a more comprehensive power reduction infrastructure to reduce power-limited yield, results on reliability-limited versus power-limited yield, and a characterization effort for exploring even higher frequencies, with our first reported 6-GHz values achieved in the lab at customer temperatures and voltages.