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     dc — DEC/Intel 21143 and clone 10/100 Ethernet driver


     To compile this driver into the kernel, place the following lines in your kernel
     configuration file:

           device miibus
           device dc

     Alternatively, to load the driver as a module at boot time, place the following line in



     The dc driver provides support for several PCI Fast Ethernet adapters and embedded
     controllers based on the DEC/Intel 21143 chipset and clones.

     All of supported chipsets have the same general register layout, DMA descriptor format and
     method of operation.  All of the clone chips are based on the 21143 design with various
     modifications.  The 21143 itself has support for 10baseT, BNC, AUI, MII and symbol media
     attachments, 10 and 100Mbps speeds in full or half duplex, built in NWAY autonegotiation and
     wake on LAN.  The 21143 also offers several receive filter programming options including
     perfect filtering, inverse perfect filtering and hash table filtering.

     Some clone chips duplicate the 21143 fairly closely while others only maintain superficial
     similarities.  Some support only MII media attachments.  Others use different receiver
     filter programming mechanisms.  At least one supports only chained DMA descriptors (most
     support both chained descriptors and contiguously allocated fixed size rings).  Some chips
     (especially the PNIC) also have peculiar bugs.  The dc driver does its best to provide
     generalized support for all of these chipsets in order to keep special case code to a

     These chips are used by many vendors which makes it difficult to provide a complete list of
     all supported cards.

     The dc driver supports the following media types:

     autoselect   Enable autoselection of the media type and options.  The user can manually
                  override the autoselected mode by adding media options to the /etc/rc.conf

                  Note: the built-in NWAY autonegotiation on the original PNIC 82c168 chip is
                  horribly broken and is not supported by the dc driver at this time (see the
                  BUGS section for details).  The original 82c168 appears on very early revisions
                  of the LinkSys LNE100TX and Matrox FastNIC.

     10baseT/UTP  Set 10Mbps operation.  The mediaopt option can also be used to enable
                  full-duplex operation.  Not specifying full-duplex implies half-duplex mode.

     100baseTX    Set 100Mbps (Fast Ethernet) operation.  The mediaopt option can also be used to
                  enable full-duplex operation.  Not specifying full-duplex implies half-duplex

     The dc driver supports the following media options:

     full-duplex  Force full duplex operation.  The interface will operate in half duplex mode if
                  this media option is not specified.

     Note that the 100baseTX media type may not be available on certain Intel 21143 adapters
     which support 10Mbps media attachments only.  For more information on configuring this
     device, see ifconfig(8).


     The dc driver provides support for the following chipsets:

        DEC/Intel 21143
        ADMtek AL981 Comet, AN985 Centaur, ADM9511 Centaur II and ADM9513 Centaur II
        ALi/ULi M5261 and M5263
        ASIX Electronics AX88140A and AX88141
        Conexant LANfinity RS7112 (miniPCI)
        Davicom DM9009, DM9100, DM9102 and DM9102A
        Lite-On 82c168 and 82c169 PNIC
        Lite-On/Macronix 82c115 PNIC II
        Macronix 98713, 98713A, 98715, 98715A, 98715AEC-C, 98725, 98727 and 98732
        Xircom X3201 (cardbus only)

     The following NICs are known to work with the dc driver at this time:

        3Com OfficeConnect 10/100B (ADMtek AN985 Centaur-P)
        Abocom FE2500
        Accton EN1217 (98715A)
        Accton EN2242 MiniPCI
        Adico AE310TX (98715A)
        Alfa Inc GFC2204 (ASIX AX88140A)
        Built in 10Mbps only Ethernet on Compaq Presario 7900 series desktops (21143, non-MII)
        Built in Sun DMFE 10/100 Mbps Ethernet on Sun Netra X1 and Sun Fire V100 (DM9102A, MII)
        Built in Ethernet on LinkSys EtherFast 10/100 Instant GigaDrive (DM9102, MII)
        CNet Pro110B (ASIX AX88140A)
        CNet Pro120A (98715A or 98713A) and CNet Pro120B (98715)
        Compex RL100-TX (98713 or 98713A)
        D-Link DFE-570TX (21143, MII, quad port)
        Digital DE500-BA 10/100 (21143, non-MII)
        ELECOM Laneed LD-CBL/TXA (ADMtek AN985)
        Hawking CB102 CardBus
        IBM EtherJet Cardbus Adapter
        Intel PRO/100 Mobile Cardbus (versions that use the X3201 chipset)
        Jaton XpressNet (Davicom DM9102)
        Kingston KNE100TX (21143, MII)
        Kingston KNE110TX (PNIC 82c169)
        LinkSys LNE100TX (PNIC 82c168, 82c169)
        LinkSys LNE100TX v2.0 (PNIC II 82c115)
        LinkSys LNE100TX v4.0/4.1 (ADMtek AN985 Centaur-P)
        Matrox FastNIC 10/100 (PNIC 82c168, 82c169)
        Melco LGY-PCI-TXL
        Microsoft MN-120 10/100 CardBus (ADMTek Centaur-C)
        Microsoft MN-130 10/100 PCI (ADMTek Centaur-P)
        NDC SOHOware SFA110A (98713A)
        NDC SOHOware SFA110A Rev B4 (98715AEC-C)
        NetGear FA310-TX Rev. D1, D2 or D3 (PNIC 82c169)
        Netgear FA511
        PlaneX FNW-3602-T (ADMtek AN985)
        SMC EZ Card 10/100 1233A-TX (ADMtek AN985)
        SVEC PN102-TX (98713)
        Xircom Cardbus Realport
        Xircom Cardbus Ethernet 10/100
        Xircom Cardbus Ethernet II 10/100


     On sparc64 the dc driver respects the local-mac-address? system configuration variable for
     the built in Sun DMFE 10/100 Mbps Ethernet interfaces on Sun Netra X1 and Sun Fire V100.
     This system configuration variable can be set in the Open Firmware boot monitor using the
     setenv command or by eeprom(8).  If set to “false” (the default), the dc driver will use the
     system's default MAC address for both of the built in devices.  If set to “true”, the unique
     MAC address of each interface is used rather than the system's default MAC address.


     dc%d: couldn't map ports/memory  A fatal initialization error has occurred.

     dc%d: couldn't map interrupt  A fatal initialization error has occurred.

     dc%d: watchdog timeout  A packet was queued for transmission and a transmit command was
     issued, but the device failed to acknowledge the transmission before a timeout expired.
     This can happen if the device is unable to deliver interrupts for some reason, of if there
     is a problem with the network connection (cable or network equipment) that results in a loss
     of link.

     dc%d: no memory for rx list  The driver failed to allocate an mbuf for the receiver ring.

     dc%d: TX underrun -- increasing TX threshold  The device generated a transmit underrun error
     while attempting to DMA and transmit a packet.  This happens if the host is not able to DMA
     the packet data into the NIC's FIFO fast enough.  The driver will dynamically increase the
     transmit start threshold so that more data must be DMAed into the FIFO before the NIC will
     start transmitting it onto the wire.

     dc%d: TX underrun -- using store and forward mode  The device continued to generate transmit
     underruns even after all possible transmit start threshold settings had been tried, so the
     driver programmed the chip for store and forward mode.  In this mode, the NIC will not begin
     transmission until the entire packet has been transferred into its FIFO memory.

     dc%d: chip is in D3 power state -- setting to D0  This message applies only to adapters
     which support power management.  Some operating systems place the controller in low power
     mode when shutting down, and some PCI BIOSes fail to bring the chip out of this state before
     configuring it.  The controller loses all of its PCI configuration in the D3 state, so if
     the BIOS does not set it back to full power mode in time, it will not be able to configure
     it correctly.  The driver tries to detect this condition and bring the adapter back to the
     D0 (full power) state, but this may not be enough to return the driver to a fully
     operational condition.  If you see this message at boot time and the driver fails to attach
     the device as a network interface, you will have to perform a second warm boot to have the
     device properly configured.

     Note that this condition only occurs when warm booting from another operating system.  If
     you power down your system prior to booting FreeBSD, the card should be configured


     altq(4), arp(4), miibus(4), netintro(4), ng_ether(4), polling(4), vlan(4), eeprom(8),

     ADMtek AL981, AL983 and AL985 data sheets,

     ASIX Electronics AX88140A and AX88141 data sheets,

     Davicom DM9102 data sheet,

     Intel 21143 Hardware Reference Manual,

     Macronix 98713/A, 98715/A and 98725 data sheets,

     Macronix 98713/A and 98715/A app notes,


     The dc device driver first appeared in FreeBSD 4.0.


     The dc driver was written by Bill Paul <>.


     The Macronix application notes claim that in order to put the chips in normal operation, the
     driver must write a certain magic number into the CSR16 register.  The numbers are
     documented in the app notes, but the exact meaning of the bits is not.

     The 98713A seems to have a problem with 10Mbps full duplex mode.  The transmitter works but
     the receiver tends to produce many unexplained errors leading to very poor overall
     performance.  The 98715A does not exhibit this problem.  All other modes on the 98713A seem
     to work correctly.

     The original 82c168 PNIC chip has built in NWAY support which is used on certain early
     LinkSys LNE100TX and Matrox FastNIC cards, however it is horribly broken and difficult to
     use reliably.  Consequently, autonegotiation is not currently supported for this chipset:
     the driver defaults the NIC to 10baseT half duplex, and it is up to the operator to manually
     select a different mode if necessary.  (Later cards use an external MII transceiver to
     implement NWAY autonegotiation and work correctly.)

     The dc driver programs 82c168 and 82c169 PNIC chips to use the store and forward setting for
     the transmit start threshold by default.  This is to work around problems with some NIC/PCI
     bus combinations where the PNIC can transmit corrupt frames when operating at 100Mbps,
     probably due to PCI DMA burst transfer errors.

     The 82c168 and 82c169 PNIC chips also have a receiver bug that sometimes manifests during
     periods of heavy receive and transmit activity, where the chip will improperly DMA received
     frames to the host.  The chips appear to upload several kilobytes of garbage data along with
     the received frame data, dirtying several RX buffers instead of just the expected one.  The
     dc driver detects this condition and will salvage the frame; however, it incurs a serious
     performance penalty in the process.

     The PNIC chips also sometimes generate a transmit underrun error when the driver attempts to
     download the receiver filter setup frame, which can result in the receive filter being
     incorrectly programmed.  The dc driver will watch for this condition and requeue the setup
     frame until it is transferred successfully.

     The ADMtek AL981 chip (and possibly the AN985 as well) has been observed to sometimes wedge
     on transmit: this appears to happen when the driver queues a sequence of frames which cause
     it to wrap from the end of the transmit descriptor ring back to the beginning.  The dc
     driver attempts to avoid this condition by not queuing any frames past the end of the
     transmit ring during a single invocation of the dc_start() routine.  This workaround has a
     negligible impact on transmit performance.