IBM S822LC, Technical Overview And Introduction

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IBM Power Systems S822LC for High Performance Computing
򐂰 Hardware data prefetching with 16 independent data streams and software control
򐂰 Hardware decimal floating point (DFP) capability.
More information about Power ISA Version 2.07 can be found at the following website:
https://www.power.org/wp-content/uploads/2013/05/PowerISA_V2.07_PUBLIC.pdf
Figure 1-7 shows a picture of the POWER8 core, with some of the functional units
highlighted.
Figure 1-7 POWER8 processor core
1.7.3 Simultaneous multithreading
Simultaneous multithreading (SMT) allows a single physical processor core to dispatch
simultaneously instructions from more than one hardware thread context. With SMT, each
POWER8 core can present eight hardware threads. Because there are multiple hardware
threads per physical processor core, additional instructions can run at the same time. SMT is
primarily beneficial in commercial environments where the speed of an individual transaction
is not as critical as the total number of transactions that are performed. SMT typically
increases the throughput of workloads with large or frequently changing working sets, such
as database servers and web servers.
Table 1-4 shows a comparison between the different POWER processors options for a
Power S822LC server and the number of threads that are supported by each SMT mode.
Table 1-4 SMT levels that are supported by a Power S822LC server
Cores per system SMT mode Hardware threads per system
16 Single Thread (ST) 16
16 SMT2 32
16 SMT4 64
16 SMT8 128
20 Single Thread (ST) 20
20 SMT2 40
20 SMT4 80