into a backplane or motherboard. Figure 3 shows the
PEX 8512 in this application.
x4
Quad GE
x4
PEX 8512
x4
Quad GE
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 8512
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.
The redundancy of the host and the fabric can be achieved
through many possible configurations using NTB function of
PEX 8512. 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 8512 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.
Intelligent Adapter Card
The PEX 8512 supports the
non-transparency
feature.
Figure 4 illustrates a host system using an intelligent adapter
card.
Intelligent I/O Adaptor
x2
Non-Transparent
Port
Figure 5. Dual Host/Fabric Mode
I/O
CPU
x2
I/O
x4
NT
Primary
Primary
Host
Host
Expansion Application
The PEX 8512 can also be utilized to expand the number of
PCI Express devices in a given system. Figure 6 shows how
the PEX 8512 can be used to double the number of ports
available from the Root Complex. Each port in the PEX 8512
is configured with a x4 link width. The Peer-to-peer
communication feature of the PEX 8512 allows the PCI
Express I/O devices to communicate with each other without
any centralized control.
CPU
Root
Complex
CPU
Blade
I/O
x2
PEX 8512
I/O
I/O
I/O
x2
PEX 8533
Figure 4. Intelligent Adapter Usage
In this figure, the CPU on the adapter card is isolated from the
host CPU. The PEX 8512 non-transparent port allows the two
CPUs to be isolated but communicate with each other through
various registers that are designed in the PEX 8512 for that
purpose. The host CPU
can dynamically re-assign both the
upstream port and the non-transparent port
of PEX 8512
allowing the system to be reconfigured.
x4
PEX 8512
x2
x2
x2
x2
x4
PEX 8512
x4
x4
Dual GE
Dual GE
Dual GE
Dual GE
FC
Dual Host/Fabric Model
The
ExpressLane
PEX 8512 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.
PCI Express
Slot
Figure 6. Expansion Application
PLX [ PLX TECHNOLOGY ]
