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DC(4)                    BSD Kernel Interfaces Manual                    DC(4)

     dc -- DEC/Intel 21140/21142/21143/21145 and clones 10/100 Ethernet device

     dc* at pci?
     dc* at cardbus?
     amphy* at mii?
     bmtphy* at mii?
     dcphy* at mii?
     icsphy* at mii?
     lxtphy* at mii?
     mtdphy* at mii?
     nsphy* at mii?
     nsphyter* at mii?
     sqphy* at mii?
     tqphy* at mii?

     The dc driver provides support for several PCI, Mini PCI, and CardBus
     Fast Ethernet adapters and embedded controllers based on the following

           o   DEC 21140 PCI
           o   DEC/Intel 21143 PCI and CardBus
           o   Intel 21145 PCI
           o   Macronix 98713, 98713A, 98715, 98715A, 98725, 98727 and 98732
           o   Davicom DM9100, DM9102, and DM9102A
           o   ASIX Electronics AX88140A and AX88141
           o   ADMtek AL981 Comet, AN983 Centaur-P and ADM9511/ADM9513 Cen-
               taur-II PCI
           o   ADMtek AN985 Centaur-C CardBus
           o   Lite-On 82c168 and 82c169 PNIC
           o   Lite-On/Macronix 82c115 PNIC II
           o   Xircom X3201-based CardBus

     All of these chips 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 21140 is an older version
     of the 21143.)  The 21143 itself has support for 10baseT, BNC, AUI, MII
     and symbol media attachments, 10 and 100Mbps speeds in full or half
     duplex, and built-in NWAY autonegotiation.  The 21143 also offers several
     receive filter programming options including perfect filtering, inverse
     perfect filtering and hash table filtering.  The 21145 seems to be 10Mbps
     only and has an additional (unsupported) HomePNA PHY.

     Some clone chips duplicate the 21143 fairly closely while others only
     maintain superficial similarities.  Some support only MII media attach-
     ments.  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 minimum.

     These chips are used by many vendors, which makes it difficult to provide
     a complete list of all supported cards.  The following NICs are known to
     work with the dc driver at this time:

           o   Digital DE500-BA 10/100 (21143, non-MII)
           o   Built-in DE500-BA on DEC Alpha workstations (21143, non-MII)
           o   Built-in Ethernet on Linksys EtherFast 10/100 Instant GigaDrive
               (DM9102, MII)
           o   Kingston KNE100TX (21143, MII)
           o   D-Link DFE-570TX (21143, MII, quad port)
           o   NDC SOHOware SFA110A (98713A)
           o   NDC SOHOware SFA110A Rev B4 (98715AEC-C)
           o   SVEC PN102-TX (98713)
           o   CNet Pro120A (98715A or 98713A) and CNet Pro120B (98715)
           o   Compex RL100-TX (98713 or 98713A)
           o   Linksys LNE100TX (PNIC 82c168, 82c169)
           o   NetGear FA310-TX Rev. D1, D2 or D3 (PNIC 82c169)
           o   Matrox FastNIC 10/100 (PNIC 82c168, 82c169)
           o   Kingston KNE110TX (PNIC 82c169)
           o   Linksys LNE100TX v2.0 (PNIC II 82c115)
           o   Jaton XpressNet (Davicom DM9102)
           o   Alfa Inc GFC2204 (ASIX AX88140A)
           o   CNet Pro110B (ASIX AX88140A)
           o   Linksys LNE100TX v4.x (ADMtek AN983 Centaur-P)
           o   Xircom CardBus, including RealPort models (Xircom X3201)
           o   IBM EtherJet 10/100 CardBus (Intel 21143)
           o   Accton EN1217 (98715) and EN2242 (ADMtek Centaur)
           o   Mototech ME316 (ADMtek Centaur)
           o   Conexant LANfinity RS7112 Mini PCI

     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 hostname.if(5) file.

                  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: the chip will operate in any speed
                  or duplex mode, however these must be set manually.  The
                  original 82c168 appears on very early revisions of the
                  Linksys LNE100TX and Matrox FastNIC.

     10baseT      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 spec-
                  ifying full duplex implies half-duplex mode.

     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.  The Intel
     21145 supports 10Mbps half-duplex only.

     For more information on configuring this device, see ifconfig(8).

     dc0: couldn't map ports/memory  A fatal initialization error has

     dc0: couldn't map interrupt  A fatal initialization error has occurred.

     dc0: watchdog timeout  A packet was queued for transmission and a trans-
     mit command was issued, however 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, or if there is a problem
     with the network connection (cable).

     dc0: no memory for rx list  The driver failed to allocate an mbuf for the
     receiver ring.

     dc0: 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 trans-
     mit start threshold so that more data must be DMAed into the FIFO before
     the NIC will start transmitting it onto the wire.

     dc0: 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 transmis-
     sion until the entire packet has been transferred into its FIFO memory.

     amphy(4), arp(4), bmtphy(4), cardbus(4), dcphy(4), icsphy(4), ifmedia(4),
     intro(4), lxtphy(4), mtdphy(4), netintro(4), nsphy(4), nsphyter(4),
     pci(4), sqphy(4), tqphy(4), hostname.if(5), ifconfig(8)

     ADMtek AL981 and AL983 data sheets, http://www.admtek.com.tw.

     ASIX Electronics AX88140A and AX88141 data sheets,

     Davicom DM9102 data sheet, http://www.davicom8.com.

     Intel 21143 Hardware Reference Manual, http://developer.intel.com.

     Macronix 98713/A, 98715/A and 98725 data sheets, http://www.macronix.com.

     Macronix 98713/A and 98715/A app notes, http://www.macronix.com.

     The dc device driver first appeared in FreeBSD 4.0.  OpenBSD support was
     added in OpenBSD 2.7.

     The dc driver was written by Bill Paul <wpaul@ee.columbia.edu> and ported
     to OpenBSD by Aaron Campbell <aaron@openbsd.org>.

     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 cor-

     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, autonegoti-
     ation is not currently supported for this chipset: the driver defaults
     the NIC to 10baseT half duplex, and it's 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 AN983 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.

     The mii_tick() function does not currently run for ASIX boards, meaning
     cable disconnects and reconnects can go unnoticed.  The AX88140A and
     AX88141 data sheets indicate that they don't have RX or TX state regis-
     ters (the bits are reserved).  Therefore, we can't seem to reliably
     detect when the adapter is idle.

     The Davicom interfaces require a grossly high PCI latency timer value to
     function properly.  This means when a Davicom adapter is present in the
     machine, it is given an unfairly high amount of bandwidth on the PCI bus,
     unnecessarily taking time away from other devices.  Therefore, Davicom
     network cards are not recommended for use with OpenBSD.  Be careful; some
     motherboards have Davicom interfaces built-in.

BSD                             August 14, 2013                            BSD