2.7 IBM z15: A 12-Core 5.2GHz Microprocessor

The latest IBM Z microprocessor in the z15 system has been redesigned to have improved performance, system capacity and security over the previous z14 system [1]. These achievements are made while maintaining the central processor (CP) and system controller (SC) chip die sizes at 696mm
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in the GlobalFoundries 14nm high performance (14HP) SOI FinFET technology and 17 layers of copper interconnect [2], both design points of the z14 system. The system contains up to 20 CP and 5 SC chips. Each CP, shown in die photo A (Fig. 2.7.7), operates at 5.2GHz and is comprised of 12 cores, 3 PCle Gen4 interfaces, 256MB of L3 embedded DRAM (eDRAM) cache, two X-BUS interfaces connecting to one other CP chip and one SC chip, and a redundant array of independent memory (RAIM) interface. Each core on the CP chip has 8MB of L2 eDRAM cache as well as 256KB of L1 SRAM cache, both caches split evenly between data and instruction. Each SC, shown in die photo B, operates at half the frequency of the CP, or 2.6GHz, has 960MB of L4 eDRAM cache, X-BUS interfaces connecting to half of the CP chips in the drawer and four A-BUS interfaces connecting to the SC chips on the other drawers in the system. The CP contains 9.2B transistors and the SC contains 12.2B transistors. The total 10 bandwidth of the CP and SC are 2.3Tb/s and 5.6Tb/s, respectively.