IBM S822LC, Technical Overview And Introduction

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IBM Power Systems S822LC for High Performance Computing
1.9 System bus
This section provides more information about the internal buses.
The Power S822LC servers have internal I/O connectivity through Peripheral Component
Interconnect Express Gen3 (PCI Express Gen3 or PCIe Gen3) slots.
The internal I/O subsystem on the systems is connected to the PCIe controllers on a
POWER8 processor in the system. Each POWER8 processor has a bus that has 32 PCIe
lanes running at 9.6 Gbps full-duplex and provides 64 GBps of I/O connectivity to the PCIe
slots, SAS internal adapters, and USB ports.
Some PCIe devices are connected directly to the PCIe Gen3 buses on the processors, and
other devices are connected to these buses through PCIe Gen3 Switches. The PCIe Gen3
switches are high-speed devices (512 GBps - 768 GBps each) that allow for the optimal
usage of the processors PCIe Gen3 x16 buses by grouping slower x8 or x4 devices that might
plug into a x8 slot and not use its full bandwidth. For more information about which slots are
connected directly to the processor and which ones are attached to PCIe Gen3 switches
(referred as PLX), see 1.7, “The POWER8 processor” on page 9.