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+Linux and the 3Com EtherLink III Series Ethercards (driver v1.18c and higher)
+----------------------------------------------------------------------------
+
+This file contains the instructions and caveats for v1.18c and higher versions
+of the 3c509 driver. You should not use the driver without reading this file.
+
+release 1.0
+28 February 2002
+Current maintainer (corrections to):
+  David Ruggiero <jdr@farfalle.com>
+
+----------------------------------------------------------------------------
+
+(0) Introduction
+
+The following are notes and information on using the 3Com EtherLink III series
+ethercards in Linux. These cards are commonly known by the most widely-used
+card's 3Com model number, 3c509. They are all 10mb/s ISA-bus cards and shouldn't
+be (but sometimes are) confused with the similarly-numbered PCI-bus "3c905"
+(aka "Vortex" or "Boomerang") series.  Kernel support for the 3c509 family is
+provided by the module 3c509.c, which has code to support all of the following
+models:
+
+  3c509 (original ISA card)
+  3c509B (later revision of the ISA card; supports full-duplex)
+  3c589 (PCMCIA)
+  3c589B (later revision of the 3c589; supports full-duplex)
+  3c529 (MCA)
+  3c579 (EISA)
+
+Large portions of this documentation were heavily borrowed from the guide
+written the original author of the 3c509 driver, Donald Becker. The master
+copy of that document, which contains notes on older versions of the driver,
+currently resides on Scyld web server: http://www.scyld.com/network/3c509.html.
+
+
+(1) Special Driver Features
+
+Overriding card settings
+
+The driver allows boot- or load-time overriding of the card's detected IOADDR,
+IRQ, and transceiver settings, although this capability shouldn't generally be
+needed except to enable full-duplex mode (see below). An example of the syntax
+for LILO parameters for doing this:
+
+    ether=10,0x310,3,0x3c509,eth0 
+
+This configures the first found 3c509 card for IRQ 10, base I/O 0x310, and
+transceiver type 3 (10base2). The flag "0x3c509" must be set to avoid conflicts
+with other card types when overriding the I/O address. When the driver is
+loaded as a module, only the IRQ and transceiver setting may be overridden.
+For example, setting two cards to 10base2/IRQ10 and AUI/IRQ11 is done by using
+the xcvr and irq module options:
+
+   options 3c509 xcvr=3,1 irq=10,11
+
+
+(2) Full-duplex mode
+
+The v1.18c driver added support for the 3c509B's full-duplex capabilities.
+In order to enable and successfully use full-duplex mode, three conditions
+must be met: 
+
+(a) You must have a Etherlink III card model whose hardware supports full-
+duplex operations. Currently, the only members of the 3c509 family that are
+positively known to support full-duplex are the 3c509B (ISA bus) and 3c589B
+(PCMCIA) cards. Cards without the "B" model designation do *not* support
+full-duplex mode; these include the original 3c509 (no "B"), the original
+3c589, the 3c529 (MCA bus), and the 3c579 (EISA bus).
+
+(b) You must be using your card's 10baseT transceiver (i.e., the RJ-45
+connector), not its AUI (thick-net) or 10base2 (thin-net/coax) interfaces.
+AUI and 10base2 network cabling is physically incapable of full-duplex
+operation.
+
+(c) Most importantly, your 3c509B must be connected to a link partner that is
+itself full-duplex capable. This is almost certainly one of two things: a full-
+duplex-capable  Ethernet switch (*not* a hub), or a full-duplex-capable NIC on
+another system that's connected directly to the 3c509B via a crossover cable.
+ 
+/////Extremely important caution concerning full-duplex mode/////
+Understand that the 3c509B's hardware's full-duplex support is much more
+limited than that provide by more modern network interface cards. Although
+at the physical layer of the network it fully supports full-duplex operation,
+the card was designed before the current Ethernet auto-negotiation (N-way)
+spec was written. This means that the 3c509B family ***cannot and will not
+auto-negotiate a full-duplex connection with its link partner under any
+circumstances, no matter how it is initialized***. If the full-duplex mode
+of the 3c509B is enabled, its link partner will very likely need to be
+independently _forced_ into full-duplex mode as well; otherwise various nasty
+failures will occur - at the very least, you'll see massive numbers of packet
+collisions. This is one of very rare circumstances where disabling auto-
+negotiation and forcing the duplex mode of a network interface card or switch
+would ever be necessary or desirable.
+
+
+(3) Available Transceiver Types
+
+For versions of the driver v1.18c and above, the available transceiver types are:
+ 
+0  transceiver type from EEPROM config (normally 10baseT); force half-duplex
+1  AUI (thick-net / DB15 connector)
+2  (undefined)
+3  10base2 (thin-net == coax / BNC connector)
+4  10baseT (RJ-45 connector); force half-duplex mode
+8  transceiver type and duplex mode taken from card's EEPROM config settings
+12 10baseT (RJ-45 connector); force full-duplex mode
+
+Prior to driver version 1.18c, only transceiver codes 0-4 were supported. Note
+that the new transceiver codes 8 and 12 are the *only* ones that will enable
+full-duplex mode, no matter what the card's detected EEPROM settings might be.
+This insured that merely upgrading the driver from an earlier version would
+never automatically enable full-duplex mode in an existing installation;
+it must always be explicitly enabled via one of these code in order to be
+activated.
+  
+
+(4a) Interpretation of error messages and common problems
+
+Error Messages
+
+eth0: Infinite loop in interrupt, status 2011. 
+These are "mostly harmless" message indicating that the driver had too much
+work during that interrupt cycle. With a status of 0x2011 you are receiving
+packets faster than they can be removed from the card. This should be rare
+or impossible in normal operation. Possible causes of this error report are:
+ 
+   - a "green" mode enabled that slows the processor down when there is no
+     keyboard activitiy. 
+
+   - some other device or device driver hogging the bus or disabling interrupts.
+     Check /proc/interrupts for excessive interrupt counts. The timer tick
+     interrupt should always be incrementing faster than the others. 
+
+No received packets 
+If a 3c509, 3c562 or 3c589 can successfully transmit packets, but never
+receives packets (as reported by /proc/net/dev or 'ifconfig') you likely
+have an interrupt line problem. Check /proc/interrupts to verify that the
+card is actually generating interrupts. If the interrupt count is not
+increasing you likely have a physical conflict with two devices trying to
+use the same ISA IRQ line. The common conflict is with a sound card on IRQ10
+or IRQ5, and the easiest solution is to move the 3c509 to a different
+interrupt line. If the device is receiving packets but 'ping' doesn't work,
+you have a routing problem.
+
+Tx Carrier Errors Reported in /proc/net/dev 
+If an EtherLink III appears to transmit packets, but the "Tx carrier errors"
+field in /proc/net/dev increments as quickly as the Tx packet count, you
+likely have an unterminated network or the incorrect media transceiver selected. 
+
+3c509B card is not detected on machines with an ISA PnP BIOS. 
+While the updated driver works with most PnP BIOS programs, it does not work
+with all. This can be fixed by disabling PnP support using the 3Com-supplied
+setup program. 
+
+3c509 card is not detected on overclocked machines 
+Increase the delay time in id_read_eeprom() from the current value, 500,
+to an absurdly high value, such as 5000. 
+
+
+(4b) Decoding Status and Error Messages
+
+The bits in the main status register are: 
+
+value   description
+0x01    Interrupt latch
+0x02    Tx overrun, or Rx underrun
+0x04    Tx complete
+0x08    Tx FIFO room available
+0x10    A complete Rx packet has arrived
+0x20    A Rx packet has started to arrive
+0x40    The driver has requested an interrupt
+0x80    Statistics counter nearly full
+
+The bits in the transmit (Tx) status word are: 
+
+value   description
+0x02    Out-of-window collision.
+0x04    Status stack overflow (normally impossible).
+0x08    16 collisions.
+0x10    Tx underrun (not enough PCI bus bandwidth).
+0x20    Tx jabber.
+0x40    Tx interrupt requested.
+0x80    Status is valid (this should always be set).
+
+
+When a transmit error occurs the driver produces a status message such as 
+
+   eth0: Transmit error, Tx status register 82
+
+The two values typically seen here are:
+
+0x82 
+Out of window collision. This typically occurs when some other Ethernet
+host is incorrectly set to full duplex on a half duplex network. 
+
+0x88 
+16 collisions. This typically occurs when the network is exceptionally busy
+or when another host doesn't correctly back off after a collision. If this
+error is mixed with 0x82 errors it is the result of a host incorrectly set
+to full duplex (see above).
+
+Both of these errors are the result of network problems that should be
+corrected. They do not represent driver malfunction.
+
+
+(5) Revision history (this file)
+
+28Feb02 v1.0  DR   New; major portions based on Becker original 3c509 docs
+