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Adapter configurations 84
o
Default: 8, corresponding to 32 bytes or 8 dwords in the receive FIFO.
o Normal Behavior: No message will be displayed. The driver will use the specified value to
configure.
o Possible Errors: If the RXFIFO parameter is set to an invalid value, the parameter is ignored and
the default value is used, and a message indicates a "Parameter value out of range" error.
• TXFIFO
o Syntax: TXFIFO=[0..15 | 0x0..0xF]
o Example: TXFIFO=8
o Default: 8, corresponding to 32 bytes or 8 dwords in the transmit FIFO.
o Normal Behavior: No message will be displayed. The driver will use the specified value to
configure.
o Possible Errors: If the TXFIFO parameter is set to an invalid value, the parameter is ignored and
the default value is used, and a message indicates a "Parameter value out of range" error.
• TXTHRESHOLD
o Syntax: TXTHRESHOLD=[0..254 | 0x0..0xFE]
o Example: TXTHRESHOLD=32
o Default: 32, corresponding to 32 * 8=256 bytes
o Normal Behavior: The value will be set in every transmit command. The initial value can only be
changed at load time, although the driver will increase the value if underruns are detected.
Setting a low value (less than 16) in high bus latency systems could cause excessive TX DMA
underruns, reducing throughput until the driver reacts. Setting a value of more than 200
completely eliminates the possibility of TX DMA underruns.
o Possible Errors:
If the TXTHRESHOLD parameter is set to an invalid value, the parameter is ignored and the
default value is used, and a message indicates a "Parameter value out of range" error.
• IFS
o Syntax: IFS=[0..255 | 0x0..0xFF]
o Example: IFS=16
o Default: 0 (minimum spacing between frames)
o Normal Behavior: The value will be used to configure the 82557 at initialization time. A value of
0 implies minimum IFS between 2 transmit frames. Increasing the value reduces the probability of
collisions under heavy load due to multiple clients, but will have a negative impact on transmit
throughput in a point-to-point single-client packet burst.
o Possible Errors: If the IFS parameter is set to an invalid value, the parameter is ignored and the
default value is used, and a message indicates a "Parameter value out of range" error.
• RXDMACOUNT
o Syntax: RXDMACOUNT=[0..127 | 0x0..0x7F]
o Example: RXDMACOUNT=16
o Default: 0 implying that the Rx DMA will continue until it is done. No other DMA request can
preempt it.