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EC(4)                     NetBSD Programmer's Manual                     EC(4)


NAME

     ec - device driver for 3Com Etherlink II (3c503) Ethernet cards


SYNOPSIS

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


DESCRIPTION

     The ec device driver supports 3Com Etherlink II (3c503) Ethernet cards.


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 tran-
     sciever.  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
     listed IRQs was specified in the kernel configuration file.  The Ether-
     link II hardware only supports the above listed IRQs.

     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 conflicting iomem address.

     ec0: warning - receiver ring buffer overrun  The DP8390 Ethernet chip
     used by this board implements a shared-memory ring-buffer to store incom-
     ing 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 some-
     times 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 occassionally overrun.  When this happens, the board must be reset
     to avoid a lockup problem in early revision 8390's.  Resetting the board
     causes all of the data in the ring-buffer to be lost, requiring it to be
     retransmitted/received, congesting the board further.  Because of this,
     maximum throughput on these boards is only about 400-600k per second.

     This problem is exasperated by NFS because the 8bit boards lack suffi-
     cient 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 NFS -r and -w options in /etc/fstab to limit NFS's packet size.
     4096k byte packets generally work.


SEE ALSO

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

NetBSD 1.4                     October 20, 1997                              1