EC(4)							   BSD Kernel Interfaces Manual 						     EC(4)

NAME

     ec -- driver for 3Com EtherLink II (3c503) ISA bus Ethernet cards

SYNOPSIS

     ec0 at isa? port 0x250 iomem 0xd8000 irq 9

DESCRIPTION

     The ec device driver supports 3Com EtherLink II (3c503) Ethernet cards for ISA bus which are based on the National Semiconductor
     DP8390/WD83C690 Ethernet interface chips.

MEDIA SELECTION

     The EtherLink II supports two media types on a single card.  All support the AUI media type.  The other media is either BNC or UTP behind a
     transceiver.  Software cannot differentiate between BNC and UTP cards.

     To enable the AUI media, select the 10base5 or aui media type with ifconfig(8)'s media directive.	To select the other media (BNC or UTP),
     select the 10base2 or bnc media type.

DIAGNOSTICS

     ec0: wildcarded IRQ is not allowed

     The IRQ was wildcarded in the kernel configuration file.  This is not supported.

     ec0: invalid IRQ <n>, must be 3, 4, 5, or 9

     An IRQ other than the above IRQ values was specified in the kernel configuration file.  The EtherLink II hardware only supports the above
     listed IRQ values.

     ec0: failed to clear shared memory at offset <off>

     The memory test was unable to clear shared the interface's shared memory region.  This often indicates that the card is configured at a con-
     flicting iomem address.

     ec0: warning - receiver ring buffer overrun

     The DP8390 Ethernet chip used by this board implements a shared-memory ring-buffer to store incoming packets.  The 3c503 usually has only 8K
     bytes of shared memory.  This is only enough room for about 4 full-size (1500 byte) packets.  This can sometimes be a problem, especially on
     the original 3c503, because these boards' shared-memory access speed is quite slow; typically only about 1MB/second.  The overhead of this
     slow memory access, and the fact that there is only room for 4 full-sized packets means that the ring-buffer will occasionally overrun.

     When an overrun occurs, the board must be reset to avoid a lockup problem in early revision DP8390 Ethernet chips.  Resetting the board
     causes all of the data in the ring-buffer to be lost, requiring the data to be retransmitted/received, congesting the board further.  Because
     of this, maximum throughput on these boards is only about 400-600K bytes per second.

     This problem is exacerbated by NFS because the 8-bit boards lack sufficient packet buffer memory to support the default 8K byte packets that
     NFS and other protocols use as their default.  If these cards must be used with NFS, use the mount_nfs(8) -r and -w options in /etc/fstab to
     limit NFS's packet size.  4K (4096) byte packets generally work.

SEE ALSO

     ifmedia(4), intro(4), isa(4), ifconfig(8), mount_nfs(8)

BSD
								 October 20, 1997							       BSD