Sun Microsystems none manual Lancemode

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By default, the driver sets ipg1 to 8-byte time and ipg2 to 4-byte time, which are the standard values. (Byte time is the time it takes to transmit one byte on the link, with a link speed of either 100 Mbps or 10 Mbps.)

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 Fast Ethernet Parallel Port SCSI (FEPS) 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 set the additional delay with 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.

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Platform Notes: The hme Fast Ethernet Device Driver—May 1996

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Contents PlatformNotesThehmeFast Ethernet Device Driver Please Recycle Page Page Contents Setting Parameters Contents Vii Viii Introduction to the hme Fast Ethernet Device Driver Related DocumentationTypographic Conventions Describes the typographic conventions used in this bookShell Prompts in Command Examples Ordering Sun DocumentsSun Welcomes Your Comments Hme Device Driver Hardware OverviewOperating Speeds and Modes Auto-NegotiationInternal Transceiver External TransceiverPlatform Notes The hme Fast Ethernet Device Driver-May Parameter Definitions Driver Parameter Values and DefinitionsRead only Local transceiver auto negotiation Capability Defining the Current Status Inter-Packet Gap ParametersLancemode Operational Mode Parameters Defines the lancemode and ipg0 parametersSelecting the Internal or External Transceiver Defining the Number of Back-to-Back Packets To Transmit Reporting Transceiver CapabilitiesReporting the Link Partner Capabilities Describes the read-only link partner capabilities= No 100Mbit/sec half-duplex transmission Platform Notes The hme Fast Ethernet Device Driver-May Setting Parameters Parameter OptionsTo specify the device instance for the ndd utility Setting Parameters Using nddIdentifying Device Instances Non-Interactive and Interactive Modes To modify a parameter valueTo modify a parameter value in interactive mode To display the value of a parameterTo list all the parameters supported by the hme driver Refer to -1 through 3-8 for parameter descriptionsSetting Forced Mode To set the mode to auto-negotiationSetting Parameters in the /etc/system File Configuring TCP/IP for Maximum PerformanceTo benchmark the TCP/IP throughput To set the TCP hiwater marks for best performanceTo set the ipg1 to 10 and ipg2 to 5 when you reboot Setting Parameters Using the hme.conf File Specify name=hme and class=sbus

none specifications

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