adapter cards with PCI Express capability. The PEX 8517 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
8517 in this application.
Dual Host/Fabric Model
The
ExpressLane
PEX 8517 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 the Non-
Transparent Bridge (NTB) function of PEX 8517. In the
configuration shown below, Host 1 controls Switch 1 and its
associated I/Os while Host 2 controls Switch 2 and its
associated I/Os. The hosts and switches are isolated using
NTB functionality of PEX 8517 on the host boards. If one of
the hosts fails the surviving host can remove the failing host
from the configuration and gain control of both 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 through the 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. Alternatively,
the PEX 8517 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 8517 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 8517 can also be utilized in embedded applications.
Figure 6 shows several independent modules connecting
through the PEX 8517. The port widths for each module can
be configured as required. The Peer-to-peer communication
feature of the PEX 8517 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 8517 non-transparent port allows the two
CPUs to be isolated but communicate with each other through
various registers that are designed in the PEX 8517 for that
purpose. The host CPU
can dynamically re-assign both the
upstream port and the non-transparent port
of PEX 8517
allowing the system to be reconfigured.
Figure 6. Embedded Systems
PLX [ PLX TECHNOLOGY ]
