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The links that are connected on the host side are called the
Primary Down Stream
Up Stream
The SuperNOVA US and downstream links each include two dedicated spare lanes. One of
these lanes is used to repair either a clock or data connection. The other lane is used only to
repair data signal defects. Each segment (host to SuperNOVA or SuperNOVA to SuperNOVA
connection) of a cascaded memory channel is independently deployed of their dedicated
spares per link. This deployment maximizes the ability to survive multiple interconnect hard
failures. The spare lanes are tested and aligned during initialization but are deactivated during
normal runtime operation. The channel frame format, error detection, and protocols are the
same before and after spare lane invocation. Spare lanes are selected by one of the following
means:
The spare lanes are selected during initialization by loading host and SuperNOVA
configuration registers based on previously logged lane failure information.
The spare lanes are selected dynamically by the hardware during runtime operation by an
error recovery operation that performs the link reinitialization and repair procedure. This
procedure is initiated by the host memory controller and supported by the SuperNOVAs in
the memory channel. During the link repair operation, the memory controller holds back
memory access requests. The procedure is designed to take less than 10 ms to prevent
system performance problems, such as timeouts.
The spare lanes are selected by system control software by loading host or SuperNOVA
configuration registers that are based on the results of the memory channel lane
shadowing diagnostic procedure.
1.4.7 Hub module
The Power 775 hub module provides all the connectivity that is needed to form a clustered
system, as shown in Figure 1-10 on page 19.
18
IBM Power Systems 775 for AIX and Linux HPC Solution
(PDS) links. The links on the cascaded side are called the
Secondary Down Stream
(SUS) and
Primary Up Stream
(SDS) links.
(PUS) and
Secondary
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