ACE(4)		      BSD/tahoe Kernel Interfaces Manual		ACE(4)

NAME
     ace — ACC 10 Mb/s Ethernet interface

SYNOPSIS
     device ace0 at vba? csr 0xffff0000 flags 0xfff80000 vector acecint
	   acerint

DESCRIPTION
     The ace interface provides access to a 10 Mb/s Ethernet network through
     an ACC controller.

     The hardware has 32 kilobytes of dual-ported memory on the VERSAbus.
     This memory is used for internal buffering by the board, and the inter‐
     face code reads the buffer contents directly through the VERSAbus.	 The
     address of this memory is given in the flags field in the configuration
     file.

     Each of the host's network addresses is specified at boot time with an
     SIOCSIFADDR ioctl(2).  The ace interface employs the address resolution
     protocol described in arp(4) to dynamically map between Internet and Eth‐
     ernet addresses on the local network.

     The interface normally tries to use a “trailer” encapsulation to minimize
     copying data on input and output.	The use of trailers is negotiated with
     ARP.  This negotiation may be disabled, on a per-interface basis, by set‐
     ting the IFF_NOTRAILERS flag with an SIOCSIFFLAGS ioctl.

     The device implements an exponential backoff algorithm when notified of a
     collision on the cable.  This algorithm utilizes a table of random num‐
     bers setup by the system at boot time.  The delay is done in the con‐
     troller.

DIAGNOSTICS
     ace%d: stray xmit interrupt, xnct %d.  An unexpected transmission com‐
     plete interrupt was received; the interrupt is ignored.

     ace%d: can't handle af%d.	The interface was handed a message with
     addresses formatted in an unsuitable address family; the packet was
     dropped.

SEE ALSO
     intro(4), inet(4), arp(4)

HISTORY
     The ace driver appeared in 4.3BSD-Tahoe.

BUGS
     The hardware is not capable of talking to itself.	The software imple‐
     ments local sending and broadcast by sending such packets to the loop
     interface.	 This is a kludge.

     The device doesn't autoconfigure its interrupt vector; it is set at 0x90
     + eight times the unit number.

4.2 Berkeley Distribution	 June 5, 1993	     4.2 Berkeley Distribution

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