PEX8632 datasheet(3/4 Pages) AVAGO

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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

Four x4 Gen1 slots

Graphics Slot

PEX 8632

Endpoint

x16

Memory

Endpoint

Gen2

Chipset

Gen2

Chipset

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).

20 AMC Blades

Fabric

Backplane

To other

Fabric

PEX 8632

CPU

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

Memory

Chipset

CPU

PEX 8632

Memory

Chipset

8 Disk Chassis

Memory

PEX 8616

8 Disk Chassis

Control

PEX 8616

Backup

System

PEX

8632

PEX

8632

Figure 6. Dual Cast in Storage Systems

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