PEX 8649, PCI Express Gen 2 Switch, 48 Lanes, 12 Ports
The PEX 8649 can also be configured in Multi-Host mode
where users can choose up to four ports as host/upstream
ports and assign a desired number of downstream ports to
each host. In Multi-Host mode, a virtual switch is created
for each host port and its associated downstream ports
inside the device. The traffic between the ports of a virtual
switch is completely isolated from the traffic in other
virtual switches. Figure 2 illustrates some configurations
of the PEX 8649 in Multi-Host mode where each ellipse
represents a virtual switch inside the device.
The PEX 8649
x8
x8
x8 x4 x4
also provides
several ways to
configure its
PEX 8649
PEX 8649
registers. The
device can be
configured
3 x8 2 x4
2 x8 2 x4 2 x4
through strapping
4 x4s
3 x4s
pins,
I
2
C
interface,
host
software, or an
optional serial
PEX 8649
PEX 8649
EEPROM. This
allows for easy
8 x4s
9 x4s
debug during the
Figure 2. Common Multi-Host Configurations
development
phase, performance monitoring during the operation phase,
and driver or software upgrade.
Multi-Host & Failover Support
In Multi-Host mode, PEX 8649 can be configured with up
to four upstream host ports, each with its own dedicated
downstream ports. The device can be configured for 1+1
redundancy or N+1 redundancy. The PEX 8649 allows the
hosts to communicate their status to each other via special
door-bell registers. In failover mode, if a host fails, the
host designated for failover will disable the upstream port
attached to the failing host and program the downstream
ports of that host to its own domain. Figure 4a shows a two
host system in Multi-Host mode with two virtual switches
inside the device and Figure 4b shows Host 1 disabled
after failure and Host 2 having taken over all of Host 1’s
end-points.
Host
1
Host
2
Host
1
Host
2
PEX 8649
PEX 8649
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
End
Point
Figure 4a. Multi-Host
Figure 4b. Multi-Host Fail-Over
Hot Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering down
the system. The PEX 8649 hot plug capability feature
makes it suitable for
High Availability (HA)
applications.
Three downstream ports include a Standard
Hot Plug Controller. If the PEX 8649 is used in an
application where one or more of its downstream ports
connect to PCI Express slots, each port’s Hot Plug
Controller can be used to manage the hot-plug event of its
associated slot. Every port on the PEX 8649 is equipped
with a hot-plug control/status register to support hot-plug
capability through external logic via the I
2
C interface.
Dual-Host & Failover Support
In Single-Host mode, the PEX 8649 supports a
Non-
Transparent (NT) Port,
which enables the
implementation of
dual-
host systems
for
redundancy and host
failover capability. The
NT port allows systems
to isolate host memory
domains by presenting
the processor subsystem
as an endpoint rather
than another
memory system.
Base address
registers are used to
translate addresses; doorbell registers are used to send
interrupts between the address domains; and scratchpad
registers (accessible by both CPUs) allow inter-processor
communication (see Figure 3).
SerDes Power and Signal Management
The PEX 8649 supports software control of the SerDes
outputs to allow optimization of power and signal strength
in a system. The PLX SerDes implementation supports
four levels of power – off, low, typical, and high. The
SerDes block also supports
loop-back modes
and
advanced reporting of error conditions,
which enables
efficient management of the entire system.
© PLX Technology, www.plxtech.com
Page 2 of 2
5/14/2009, Version 1.1
PLX [ PLX TECHNOLOGY ]
