Separate Power Backplane; Channel Topology And Emphasis Settings - Compaq BL10e - HP ProLiant - 512 MB RAM Configuration

Figure 10. Separation of the transmit and receive signal pins by a ground plane in the in c-Class enclosure
midplane
Receive Signal Pins
Interconnect Bay Connector
Transmit Signal Pins

Separate power backplane

Distributing power on the same PCB that includes the signal traces would have greatly increased the
board's complexity. Separating the power backplane from the NonStop signal midplane improves the
signal midplane by reducing its PCB thickness, reducing electrical noise (from the power components)
that would affect high-speed signals, and improving the thermal characteristics. These design choices
result in reduced cost, improved performance, and improved reliability.

Channel topology and emphasis settings

Even when using best practices, high-speed signals transmitted across multiple connectors and long
PCB traces can significantly degrade due to insertion and reflection losses. Insertion losses, such as
conductor and dielectric material losses, increase at higher frequencies. Reflection losses are due to
impedance discontinuities, primarily at connector stages. To compensate for these losses, a
transmitter's signal waveform can be shaped by selecting the signal emphasis settings. However, the
emphasis settings of a transmitter can depend on the end-to-end channel topology as well as the type
of component sending the signal. Both of these can vary in the BladeSystem c-Class because of the
flexible architecture and the use of mezzanine cards and embedded I/O devices such as network
interface controllers (NICs). As shown in Figure 11, the topology for Device 1 on server blade 1
(a-b-c) is completely different than the topology for device 1 on server blade 4 (a-d-e). Therefore, an
electronic keying mechanism in the Onboard Administrator identifies the channel topology for each
device and ensures that the proper emphasis settings are configured for that device.
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