Figure 2 shows a typical
server-based
design where the
root complex provides a PCI Express link that needs to
be expanded to a larger number of smaller ports for a
variety of I/O functions. In this example, the PEX 8548
would have a 16-lane upstream port, and as many as six
x8 or x4 downstream ports. The PEX 8548 will also
auto-negotiate down to x2 and x1 lane widths to support
endpoints requiring smaller links.
Peer-to-Peer & Backplane Usage
The PEX 8548 is also suitable for peer-to-peer
applications such as switch fabrics and backplanes.
Figure 3 represents a backplane where the device
provides peer-to-peer data exchange for a large number
of line cards where the CPU/Host plays the management
role.
CPU
Root
Complex
x16
PEX 8548
x16
x16
GPU
GPU
I/O
I/O
I/O
I/O
I/O
x8
x8
x8
Figure 4. Dual Graphics Fan-out
Power PC
x8
x8
PEX 8548
x8
Blade Server Switch Fabric
The PEX 8548 can be cascaded to create an even greater
number of ports. For example, in a Blade Server
application, two PEX 8548 switches can be combined to
support up to sixteen blades (Figure 5). The switches can
be linked to available PCI Express ports. The PEX 8508
switch can isolate each CPU blade using its Non-
Transparent Bridging function.
2 I/O Blades
CPU Blade
x8
CPU
CPU
14 CPU Blades
Figure 3. Peer-to-Peer/Backplane Usage
Graphics Fan-out Switch
The PEX 8548 offers three port configurations which are
optimal for High resolution 3D graphics applications.
Dual-graphics, high-resolution gaming, high resolution
scientific use, and image processing can benefit from its
performance features. Figure 4 illustrates usage of the
device in a dual graphics gaming application where two
GPUs 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
8548 allows the two GPU modules to communicate with
each other for maximum performance.
Root
Complex
PEX 8508
NT
PEX 8548
PEX 8548
Figure 5. Blade Server
The number of ports and port widths can be configured
as needed. This example assumes a x4 link to each CPU
blade and a x8 link to the I/O blades. The link between
the two PEX 8548 devices is x8 lanes wide.
PLX [ PLX TECHNOLOGY ]
