PEX 8696, PCI Express Gen 2 Switch, 96 Lanes, 24 Ports

variety of host-centric applications. Figure 6 shows a

server design where, in a quad or multi processor

system, users can assign endpoints/slots to CPU cores to

distribute the system load. The packets directed to

different CPUs will go to different (user assigned) PEX

8696 upstream ports, allowing better queuing and load

balancing capability for higher performance.

CPU

CPU

CPU

CPU

CPU

CPU

CPU

CPU

x8

x4s

Memory

Memory

Memory

Memory

x8s

x4

x16

Endpoint

Endpoint

Endpoint

Endpoint

Endpoint

Endpoint

Endpoint

Endpoint

PCIe Gen1 or PCIe Gen2 slots

x8

PEX 8696

PEX 8696

PEX 8696

PEX 8696

Chipset

Chipset

Chipset

Chipset

Figure 6. Host Centric Dual Upstream

Multi-Host Systems

In multi-host mode, the PEX 8696 can support up to

eight hosts at once. By creating eight virtual switches,

the PEX 8696 allows eight hosts to fan-out to their

respective endpoints. This reduces the number of

switches required for fan-out, saving precious board

space and power. In Figure 7, the PEX 8696 is being

shared by six different CPU cores (hosts) on three

servers, with each CPU core running its own

applications (I/Os). The PEX 8696 assigns the endpoints

to the appropriate host and isolates them from the other

hosts. In Figure 7, the endpoints are assigned to the CPU

core of the same color.

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

Chip

Set

Chip

Set

Chip

Set

Chip

Set

Chip

Set

Chip

Set

PEX 8696

PEX 8696

Figure 7. Multi-Host System

High-End Graphics Systems

The PEX 8696’s 96 lanes can come in handy for high-

end graphics systems, such as high-resolution gaming

and medical imaging applications, employing two or

more GPUs alongside multiple endpoints. Figure 8a

shows a dual-graphics system where the PEX 8696 is

being used to fan-out to two GPUs using x16 links and

numerous (up to 16) endpoints using x4 and x8 links.

Figure 8b, shows an ultra-gaming system using the PEX

8696 to fan-out to four GPUs via x16 links. In both

examples, two x16 upstream ports are being used. Using

PEX 8696’s multi-host capabilities, two separate virtual

hierarchies can be created, assigning GPUs & endpoints

to a particular CPU core via the x16 upstream ports.

Figure 8b. Ultra-Gaming System

x16s

Chip

Set

Chip

Set

x16s

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

PEX 8696

PEX 8696

PEX 8696

PEX 8696

Figure 8a. Dual-Graphics System

x4s

& x8s

Chip

Set

Chip

Set

x16s

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

GPU

GPU

GPU

GPU

GPU

GPU

GPU

GPU

PEX 8696

PEX 8696

PEX 8696

PEX 8696

x16s

Host Failover

The PEX 8696 can also be utilized in applications where

host failover is required. In the below application

(Figure 9), two hosts may be active simultaneously and

controlling their own domains while exchange status

information through doorbell registers or I

The devices can be programmed to trigger fail-over if

the heartbeat information is not provided. In the event of

a failure, the surviving device will reset the endpoints

connected to the failing CPU and enumerate them in its

own domain without impacting the operation of

endpoints already in its domain.

CPU

CPU

CPU

CPU

CPU

CPU

CPU

CPU

x8

x4 & x8

Chipset

Chipset

Chipset

Chipset

PEX 8696

PEX 8696

PEX 8696

PEX 8696

CPU

CPU

CPU

CPU

CPU

CPU

CPU

CPU

x8

Chipset

Chipset

Chipset

Chipset

PEX 8696

PEX 8696

PEX 8696

PEX 8696

x8s

Figure 9. Host Fail-Over

© PLX Technology, www.plxtech.com

Page 4 of 4

5/14/2009, Version 1.1