IBM Power Systems 775 Manual page 34

The hub features the following primary functions:
Connects the QCM Processor/Memory subsystem to up to two high-performance 16x
PCIe slots and one high-performance 8x PCI Express slot. This configuration provides
general-purpose I/O and networking capability for the server node.
POWER 775 drawer: In a Power 775 drawer (CEC), the Octant 0 has 3 PCIe, in which
two PCIe are 16x and one PCIe is 8x (SRIOV Ethernet Adapter is given priority in the
8x slot.). Octants 1-7 have two PCI Express, which are 16x.
Connects eight Processor QCMs together by using a low-latency, high-bandwidth,
coherent copper fabric (L-Local buses) that includes the following features:
– Enables a single hypervisor to run across 8 QCMs, which enables a single pair of
redundant service processors to manage 8 QCMs
– Directs the I/O slots that are attached to the eight hubs to the compute power of any of
the eight QCMs that provide I/O capability where needed
– Provides a message passing mechanism with high bandwidth and the lowest possible
latency between eight QCMs (8.2 TFLOPs) of compute power
Connects four Power 775 planars via the L-Remote optical connections to create a 33
TFLOP tightly connected compute building block (SuperNode). The bi-sectional exchange
bandwidth between the four boards is 3 TBps, the same bandwidth as 1500 10 Gb
Ethernet links.
Connects up to 512 groups of four planers (SuperNodes) together via the D optical buses
with ~3 TBs of exiting bandwidth per planer.
Optical links
The Hub modules that are on the node board house optical transceivers for up to 24
L-Remote links and 16 D-Links. Each optical transceiver includes a jumper cable that
connects the transceiver to the node tailstock. The transceivers are included to facilitate cost
optimization, depending on the application. The supported options are shown in Table 1-2.
Table 1-2 Supported optical link options
SuperNode type
SuperNodes not enabled
Full SuperNodes
Some customization options are available on the hub optics module, which allow some optic
transceivers to remain unpopulated on the Torrent module if the wanted topology does not
require all of transceivers. The number of actual offering options that are deployed is
dependent on specific large customer bids.
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IBM Power Systems 775 for AIX and Linux HPC Solution
L-Remote links
0 0-16 in increments of 1
24 0-16 in increments of 1
D-Links Number of
combinations
17
17
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