Backwards Compatibility with PCIe Gen1
The PEX 8632 enables a PCIe Gen2 native chipset to
create PCIe Gen1 (2.5 Gbps) slots and/or communicate
with PCIe Gen1 endpoints. The PEX 8632 is backwards
compatible with PCIe Gen1 devices and will
automatically negotiate down to Gen1 bit-rates (2.5
Gpbs) when connected to a Gen1 endpoint. In Figure 3,
the PCIe slots connected to the PEX 8632’s downstream
ports can be populated with either PCIe Gen1 or PCIe
Gen 2 devices. Conversely, the PEX 8632 can be used to
create Gen 2 slots on a Gen 1 native Chip Set in the
same fashion.
CPU
CPU
CPU
CPU
20 AMC Blades
Fabric
To
Backplane
CPU
PEX 8632
NT
PEX 8632
To other
Fabric
Figure 5. ATCA/MicroTCA Backplane Usage
Failover Storage Systems with Dual Cast
The PEX 8632’s Dual Cast feature proves to be very
useful in storage systems. In the example shown in
Figure 6, the Dual Cast feature enables the PEX 8632 to
copy data going to its two downstream ports to the
backup system and vice versa (see yellow traffic
patterns) in one transaction as opposed to having to
execute two separate transactions to send data to the
redundant chassis. By offloading the task of backing up
data onto the secondary system, processor and system
performance is enhanced. Non-Transparent (NT) ports
are used to isolate the host domains of the backup
system from the primary system.
CPU
CPU
CPU
CPU
CPU
CPU
CPU
Gen2
Chipset
x16
Graphics Slot
x8
Memory
PEX 8632
Endpoint
Endpoint
x4
x4
Four x4 Gen1 slots
Figure 4. Creating PCIe Gen1 Slots
Backplane Communication
The PEX 8632 is also well suited for backplane
applications demanding a large number of ports. Figure
5 represents an ATCA or MicroTCA backplane
application with two switch fabric blades and multiple
AMC blades. In this example, two PEX 8632s provide
peer-to-peer data exchange for up to 20 AMC blades
connecting to the switch fabric. The PEX 8632 utilizes
its NT port to isolate the hosts on the switch fabrics and
the remaining 10 downstream ports on each switch are
used to fan-out to the 20 AMC blades (or 10 AMC
Carrier Modules).
Backup
System
CPU
Chipset
x8
Memory
Chipset
x8
Memory
x8
NT
PEX 8632
x8
x8
x8
PEX
8632
x8
NT
NT
PEX 8616
x4
FC
Control
PEX 8616
x4
FC
Control
x4
FC
Control
x4
FC
Control
8 Disk Chassis
8 Disk Chassis
Figure 6. Dual Cast in Storage Systems
PLX [ PLX TECHNOLOGY ]
