FastEthernet PCI Adapter Installation & User's Guide

If your network has systems that use longer IPG (the sum of ipg1 and ipg2) and if
those machines seem to be slow in accessing the network, increase the values of
ipg1 and ipg2 to match the longer IPGs of other machines.
Defining an Additional Delay Before Transmitting
a Packet Using lance_mode and ipg0
The PCI Fast Ethernet and Expansion (PFEX) ASIC supports a programmable mode
called lance_mode. The ipg0 parameter is associated with lance_mode.
After a packet is received with lance_mode enabled (default) an additional delay is
added by setting the ipg0 parameter before transmitting the packet. This delay, set
by the ipg0 parameter, is in addition to the delay set by the ipg1 and ipg2
parameters. The additional delay set by ipg0 helps to reduce collisions. Systems that
have lance_mode enabled might not have enough time on the network.
If lance_mode is disabled, the value of ipg0 is ignored and no additional delay is
set. Only the delays set by ipg1 and ipg2 are used. Disable lance_mode if other
systems keep sending a large number of back-to-back packets.
You can add the additional delay by setting the ipg0 parameter from 0 to 31, which
is the nibble time delay. Note that nibble time is the time it takes to transfer four bits
on the link. If the link speed is 10 Mbps, nibble time is equal to 400 ns. If the link
speed is 100 Mbps, nibble time is equal to 40 ns.
For example, if the link speed is 10 Mbps, and you set ipg0 to 20 nibble times,
multiply 20 by 400 ns to get 800 ns. If the link speed is 100 Mbps, and you set ipg0
to 30 nibble-times, multiply 30 by 40 ns to get 120 ns.
Table C–4 defines the lance_mode and ipg0 parameters.
TABLE C–4 Parameters Defining lance_mode and ipg0
Parameter Values Description
lance_mode
0
1
lance_mode disabled
lance_mode enabled (default)
ipg0
0-31
1
Additional IPG before transmitting
a packet (after receiving a packet)
1. The default value is 16 nibble-times, which is 6.4 microseconds for 10 Mbps and 0.64 microseconds for 100
Mbps.
Configuring the Quad FastEthernet Device Driver Parameters 29