PEX8796, PCI Express Gen3 Switch, 96 Lanes, 24 Ports

© PLX Technology, www.plxtech.com

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24July12; v1.2

Multi-Host Systems

In multi-host mode, the PEX8796 can support up to four

hosts at once. By creating four virtual switches, the

PEX8796 allows four 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 PEX8796 is being shared by four different

CPU cores (hosts) on three servers, with each CPU core

running its own applications (I/Os). The PEX8796

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.

Figure 7. Multi-Host System

High-End Graphics Systems

The PEX8796’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 PEX8796 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

PEX8796 to fan-out to four GPUs via x16 links. In both

examples, two x16 upstream ports are being used. Using

PEX8796’s multi-host capabilities, two separate virtual

hierarchies can be created, assigning GPUs & endpoints

to a particular CPU core via the x16 upstream ports.

Host Failover

The PEX8796 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.

Figure 9. Host Fail-Over

I/O

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PEX 8796

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