2.1 The IBM POWER9 processor2.1.1 POWER9 processor overview2.1.2 POWER9 processor core2.1.3 Simultaneous multithreading2.1.4 POWER9 compatibility modes2.1.5 Processor feature codes2.1.6 Memory access2.1.7 On-chip L3 cache innovation and intelligent caching2.1.8 Hardware transactional memory2.1.9 POWER9 accelerator processor interfaces2.1.10 Power and performance management2.1.11 Comparison of the POWER9, POWER8, and POWER7+ processors2.2 Memory subsystem2.2.1 DIMM memory riser card2.2.2 Memory placement rules2.2.3 Memory activations2.2.4 Memory throughput2.2.5 Active Memory Mirroring2.2.6 Memory error correction and recovery2.2.7 Special Uncorrectable Error handling2.3 Capacity on Demand2.3.1 Capacity on Demand: New features2.3.2 Capacity Upgrade on Demand2.3.3 Processor activations2.3.4 Elastic Capacity on Demand (Temporary)2.3.5 Utility Capacity on Demand2.3.6 Trial Capacity on Demand2.3.7 Software licensing and CoD2.3.8 Solution Edition for Healthcare2.4 System buses2.4.1 PCIe Gen42.5 PCIe adapters2.5.1 New PCIe adapter features2.5.2 PCIe2.5.3 LAN adapters2.5.4 Graphics adapters2.5.5 SAS adapters2.5.6 Fibre Channel adapters2.5.7 ASYNC adapters2.5.8 USB ports2.5.9 InfiniBand host channel adapters2.5.10 Cryptographic Coprocessor2.6 Internal storage2.6.1 Backplane features2.6.2 Internal NVMe SSD drives2.6.3 Supported RAID functions2.6.4 Easy Tier2.6.5 Media drawers2.6.6 External DVD drives2.6.7 RDX removable disk drives2.7 External I/O subsystems2.7.1 PCIe Gen3 I/O Expansion Drawer2.7.2 PCIe Gen3 I/O Expansion Drawer optical cabling2.7.3 PCIe Gen3 I/O Expansion Drawer system power control network cabling2.8 External disk subsystems2.8.1 EXP24SX and EXP12SX SAS Storage Enclosure2.8.2 IBM System Storage2.9 Operating system support2.9.1 AIX operating system2.9.2 Linux operating system2.9.3 Virtual I/O Server