The PEX 8516 can be used to create an adapter or mezzanine
card that aggregates the PCI Express devices into a single port
that can be plugged into a backplane or motherboard. Figure 3
shows the PEX 8516 in this application.
Dual Host/Fabric Model
The ExpressLane PEX 8516 supports applications requiring
dual host, host failover,
and
load-sharing
applications
through the
non-transparency
feature. Figure 5 illustrates a
dual host system with dual switch fabric in dual-star
configuration.
The redundancy of the host and the fabric can be achieved
through many possible configurations using NTB function of
PEX 8516. In the configuration shown below the host 1
controls the switch 1 and associated I/Os and the host 2
controls the switch 2 and associated I/Os. The hosts and
switches are isolated using NTB functionality of PEX 8516 on
the host boards. If one of the hosts fails the surviving host can
remove the failing host from the configuration while
controlling both the switches and all I/Os. Similarly, if one of
the switches fails the host associated with that switch can send
control messages to its I/Os through the surviving switch using
NTB function.
Figure 3. Aggregation Adapter Card
The adapter card in Figure 3 can be
transparent,
in which
case the PCI Express I/O devices are just standard I/O
endpoints such as Ethernet or Fibre Channel. Or the PEX 8516
can provide a
non-transparent
port to the system (via the
card’s edge connector). In this case, one of the PCI Express
devices can be a CPU or other “intelligent” device with on-
chip processing capability – thus needing address domain
isolation from the rest of the system. This approach is
commonly used in
RAID controllers.
Intelligent Adapter Card
The PEX 8516 supports the
non-transparency
feature. Figure
4 illustrates a host system using an intelligent adapter card.
Figure 5. Dual Host/Fabric Mode
Embedded Systems
The PEX 8516 can also be utilized in embedded applications.
Figure 6 shows several independent modules connecting
through the PEX 8516. The port widths for each module can
be configured as required. The Peer-to-peer communication
feature of the PEX 8516 allows these modules to communicate
with each other without any centralized control.
Figure 4. Intelligent Adapter Usage
In this figure, the CPU on the adapter card is isolated from the
host CPU. The PEX 8516 non-transparent port allows the two
CPUs to be isolated but communicate with each other through
various registers that are designed in the PEX 8516 for that
purpose. The host CPU
can dynamically re-assign both the
upstream port and the non-transparent port
of PEX 8516
allowing the system to be reconfigured.
Figure 6. Embedded Systems
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