GEM(4)							   BSD Kernel Interfaces Manual 						    GEM(4)

NAME

     gem -- ERI/GEM/GMAC Ethernet device driver

SYNOPSIS

     gem* at pci? dev ? function ?
     gem* at sbus? slot ? offset ?

     Configuration of PHYs may also be necessary.  See mii(4).

DESCRIPTION

     The gem driver provides support for the GMac Ethernet hardware found mostly in the last Apple PowerBooks G3s and most G4-based Apple hard-
     ware, as well as many Sun UltraSPARCs.

     Cards supported by this driver include:
	   o   Sun GEM gigabit ethernet (SX fibre variants)
	   o   Sun ERI 10/100
	   o   Apple GMAC

     The GEM family supports hardware checksumming to assist in computing IPv4 TCP checksums.  The gem driver supports this feature of the chip.
     See ifconfig(8) for information on how to enable this feature.

SEE ALSO

     bmtphy(4), ifmedia(4), intro(4), mii(4), ifconfig(8)

     Sun Microsystems, GEM Gigabit Ethernet ASIC Specification, http://www.sun.com/processors/manuals/ge.pdf.

     Sun Microsystems, Sbus GEM Specification, http://mediacast.sun.com/users/Barton808/media/gem_sbus-1.pdf.

HISTORY

     The gem device driver appeared in NetBSD 1.6.  Support for PCI SX fibre cards was added in NetBSD 5.0.  Support for SBus SX fibre cards was
     added in NetBSD 5.0.

AUTHORS

     The gem driver was written by Eduardo Horvath <eeh@NetBSD.org>.  SX fibre support was added by Julian Coleman <jdc@NetBSD.org>.  The man page
     was written by Thomas Klausner <wiz@NetBSD.org>.

BUGS

     The hardware checksumming support does not support IPv4 UDP, although this was allowed prior to NetBSD 5.0.  Also, the hardware IPv4 TCP
     receive checksumming support has bugs, so this is disabled.

     On the SX fibre variants of the hardware, the link will stay down if there is a duplex mismatch.  Also, packet transmission may fail when in
     half-duplex mode.

BSD
								September 15, 2008							       BSD