SMC Networks TigerCard 1000 - Manual (Page 40)

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ONFIGURING AND
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ESTING THE
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ETWORK
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ARD
Packet Propulsion
The Packet Propulsion configuration option sets the packet-size
threshold at which Propulsion technology is used to burst packets
across the PCI bus. Propulsion increases the throughput of small
packets by coalescing transfers across the PCI bus. This minimizes
host CPU interrupts and bus arbitrations.
Use the slider control or edit box to set the packet-size threshold
level in bytes (from 0 to 1514, or 9014 if Jumbo Frames is
selected). Packets of sizes below this threshold use the Propulsion
technique, packets above use the normal scatter-gather method.
There is a trade off between the Packet Propulsion and scatter-
gather methods. Packet Propulsion uses more bus resources
whereas scatter-gather uses more CPU resources. The optimum
setting of the threshold level for a particular environment depends
on various factors, such as the PC hardware, other devices on the
PCI bus, and the applications being run. Considering all the
variables involved, it is recommended to experiment with the
Packet Propulsion threshold to find the setting that maximizes the
performance of the TigerCard 1000 in your system.
Jumbo Frame Support
The TigerCard 1000 network card can be configured to use Jumbo
Frames. This increases the maximum Ethernet frame size from
1514 bytes up to 9014 bytes. Using Jumbo Frames greatly
reduces the packet processing overhead for the host CPU and can
boost throughput by up to 300% for bulk data transfers.
Note that to use Jumbo Frames, both communicating computers
must have network cards that support this feature. Also at full
duplex, all switches in the network between the two end
computers must be able to accept the extended frame size. With
half-duplex connections, all devices in the collision domain would
need to support Jumbo Frames. LAN partitioning, either physical