pex-8624 PLX, pex-8624 Datasheet - Page 2

• Manufacturer Part Number: pex-8624
• Description: 24-lane, 6-port Pci Express Gen 2 5.0 Gt/s Switch, 19 X 19mm Fcbga
• Manufacturer: PLX

Dual-Host & Failover Support
The PEX 8624 product supports a Non-Transparent
(NT) Port, which enables the implementation of multi-
host systems in communications, storage, 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 scratchpad
registers (accessible by both CPUs) allow inter-
processor communication (see Figure 2).
Dual Cast™
The PEX 8624 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.
Read Pacing™
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.
Hot-Plug for High Availability
Hot plug capability allows users to replace hardware
modules and perform maintenance without powering
down the system. The PEX 8624 Hot-Plug capability
feature makes it suitable for High Availability (HA)
applications. Three downstream ports include a
Standard Hot-Plug Controller. If the PEX 8624 is used in
an application where one or more of its downstream
Point
Point
Point
Point
Point
Point
Point
Point
Figure 2. Non-Transparent Port
Figure 2. Non-Transparent Port
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PEX 8624
PEX 8624
PEX 8624
PEX 8624
Complex
Complex
Complex
Complex
Complex
Complex
Primary Host
Primary Host
Primary Host
Primary Host
Primary Host
Primary Host
Point
Point
Point
Point
Point
Point
Point
Point
CPU
CPU
CPU
CPU
CPU
CPU
Root
Root
Root
Root
Root
Root
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End
NT
NT
Point
Point
Point
Point
Point
Point
Point
Point
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End
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Secondary Host
Secondary Host
Secondary Host
Secondary Host
Secondary Host
Secondary Host
Non-Transparent
Non-Transparent
CPU
CPU
CPU
CPU
CPU
CPU
Port
Port
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 8624 is
equipped with a hot-plug control/status register to
support hot-plug capability through external logic via the
I
SerDes Power and Signal Management
The PEX 8624 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.
Interoperability
The PEX 8624 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 8624 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.
Applications & Usage Models
Suitable for host-centric as well as peer-to-peer traffic
patterns, the PEX 8624 can be configured for a broad
range of form factors and applications.
Host Centric Fan-out
The PEX 8624, 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 8624 has an 8-lane
upstream port, and four downstream ports using x4 links.
The PEX 8624 can also be used to create PCIe Gen 1
(2.5 Gbps) ports. The PEX 8624 is backwards
compatible with PCIe Gen 1 devices. Therefore, the
PEX 8624 enables a Gen 2 native Chip Set to fan-out to
Gen 1 endpoints. In Figure 3, the PCIe slots connected to
the PEX 8624’s downstream ports can be populated with
either PCIe Gen 1 or PCIe Gen 2 devices. Conversely,
the PEX 8624 can also be used to create Gen 2 ports on
a Gen 1 native Chip Set in the same fashion.
2
C interface.