EC(4)                   NetBSD 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 trans-
     ceiver.  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 con-
     figuration 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 conflict-
     ing 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 sec-
     ond.

     This problem is exacerbated by NFS because the 8-bit boards lack suffi-
     cient 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)

NetBSD 5.0_STABLE              October 20, 1997              NetBSD 5.0_STABLE
