Dual-Host & Failover Support
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 8616 is
equipped with a hot-plug control/status register to
support hot-plug capability through external logic via the
I2C interface.
The PEX 8616 product supports a Non-Transparent
(NT) Port, which enables the implementation of multi-
host systems and intelligent I/O modules in storage,
communications, and blade server applications. 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
SerDes Power and Signal Management
The PEX 8616 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.
Intelligent I/O Adaptor
scratchpad
registers
Non-Transparent
Port
(accessible by
both CPUs)
allow inter-
I/O
I/O
CPU
Secondary
Secondary
Primary
Primary
Host
Host
Host
Host
processor
CPU
Blade
CPU
Blade
NT
communication
(see Figure 2).
In a two-port
Interoperability
PEX 8616
The PEX 8616 is designed to be fully compliant with the
PCI Express Base Specification r2.0, and is backwards
compatible to PCI Express Base Specification r1.1 and
r1.0a. Additionally, it supports auto-negotiation, lane
reversal, and polarity reversal. Furthermore, the PEX
8616 is designed for Microsoft Vista compliance. All
PLX switches undergo thorough interoperability testing
in PLX’s Interoperability Lab and compliance testing
at the PCI-SIG plug-fest.
configuration (as in
Figure 1), the PEX
8616 can serve as an
NT buffer, isolating
two host domains via
two x8 links.
I/O
I/O
I/O
NT
PEX 8632
Figure 2. Non-Transparent Port
Dual Cast
The PEX 8616 supports Dual Cast, a feature which
allows for the copying of data (e.g. packets) from one
ingress port to two egress ports allowing for higher
performance in dual-graphics, storage, security, and
redundant applications.
Applications & Usage Models
Suitable for host-centric as well as peer-to-peer traffic
patterns, the PEX 8616 can be configured for a broad
range of form factors and applications.
Host Centric Fan-out
Read Pacing
The PEX 8616, with its symmetric or asymmetric lane
configuration capability, allows user-specific tuning to a
variety of host-centric applications. Figure 3 shows a
typical workstation design where the root complex
provides a PCI Express link that needs to be expanded to
a larger number of smaller ports for a variety of I/O
functions. In this example, the PEX 8616 has a 4-lane
upstream port and three downstream ports using x4
links.
The Read Pacing feature allows users to throttle the
amount of read requests being made by downstream
devices. When a downstream device requests several
long reads back-to-back, the Root Complex gets tied up
in serving this downstream port. If this port has a narrow
link and is therefore slow in receiving these read packets
from the Root Complex, then other downstream ports
may become starved – thus, impacting performance. The
Read Pacing feature enhances performances by allowing
for the adequate servicing of all downstream devices.
The PEX 8616 can also be used to create PCIe Gen1 (2.5
Gbps) ports. The PEX 8616 is backwards compatible
with PCIe Gen1 devices. Therefore, the PEX 8616
enables a Gen 2 native Chip Set to fan-out to Gen 1
endpoints. In Figure 3, the PCIe slots connected to the
PEX 8616’s downstream ports can be populated with
either PCIe Gen1 or PCIe Gen 2 devices. Conversely,
the PEX 8616 can also be used to create Gen 2 ports on
a Gen 1 native Chip Set in the same fashion.
Hot Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering
down the system. The PEX 8616 hot plug capability
feature makes it suitable for High Availability (HA)
applications. Two downstream ports include a Standard
Hot Plug Controller. If the PEX 8616 is used in an
application where one or more of its downstream ports
Preliminary - PLX Confidential
PLX [ PLX TECHNOLOGY ]
