PLX Confidential

Fully Compliant Power Management

For applications that require power management, the

ExpressLane PEX 8547 device supports both link (L0,

L0s, L1, L2/L3 Ready, and L3) and device (D0 and

D3hot) power management states, in compliance with

the PCI Express power management specification.

SerDes Power and Signal Management

The ExpressLane PEX 8547 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 debug and management of the

entire system.

Applications

Targeted at high-end graphics applications, the PEX

8547 supports host-centric as well as peer-to-peer

traffic patterns.

Host-Centric Graphics Fan-out Switch

In a graphics fan-out application (see Figure 1), the PEX

8547 drives a dual-output display. The PEX 8547 will

fan out to two Graphics Modules (shown as GPUs in the

Figures) via the two x16 downstream ports while the x16

upstream port links to the Root Complex. Each graphics

module drives its

own monitor.

Increasing memory

and bandwidth

requirements have

put a strain on local

GPU memory. The

PEX 8547 allows

for highly efficient

data transfers over

the PCI Express

bus, allowing the

Graphics Module to

utilize the system

memory and render

it as if it were local

graphics memory.

In a fan-out

application such as

this one, the traffic

patterns are host-

centric, with each

Graphics Module

driving its own output.

Dual Graphics with Peer-to-Peer

Communication

High resolution 3D graphics applications can take full

advantage of the PEX 8547 three port configuration.

Applications such as high-resolution gaming, high

resolution scientific use, and image processing can

benefit from the performance of the PEX 8547 switch.

Figure 2 illustrates the use of the device in a high

resolution gaming application where two Graphics

Modules drive a single monitor for the ultimate gaming

experience. The upstream x16 port links to the Root

Complex and the two downstream ports connect to the

Graphics Modules. The peer-to-peer support of the PEX

8547 allows the two Graphics Modules to communicate

with each other for maximum performance.

In this example, the two Graphics Modules divide the

screen into a

checkerboard pattern.

In Figure 2, the screen

is divided into white

frames and blue

frames, with one GPU

managing the white

frames and the other

managing the blue

frames. This mode of

operation is referred

to as Supertiling, and

is generally the most

efficient because it

evenly divides the

processing and

graphics rendering

workload across the

two Graphics

Modules.

This usage model

calls for heavy peer-

to-peer

communication

between the two

Graphics Modules.

The PEX 8547 can also support dual-graphics solutions

running in scissor, or alternate frame-rate modes. In

each of these modes, the processing and graphics

rendering workload is shared by the Graphics Modules,

and therefore requires a great amount of peer-to-peer

communication between the Graphics Modules to

monitor each other’s progress and execution.