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.
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