September 15, 2008 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 hardware, as well as many Sun UltraSPARCs.

Cards supported by this driver include:

- Sun GEM gigabit ethernet (SX fibre variants)
- Sun ERI 10/100
- 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)

### HISTORY

The gem device driver appeared in NetBSD1.6. Support for PCI SX fibre cards was added in NetBSD4.1. Support for SBus SX fibre cards was added in NetBSD5.0.

### 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 NetBSD5.0. 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.