---
name: "cas"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["freebsd", "openbsd"]
url: "https://carta.tech/man/cas/4"
---

# cas(4)

Sun Cassini 10/100/1Gb Ethernet device

## NAME

**cas** – Sun Cassini 10/100/1Gb Ethernet device

## SYNOPSIS

**cas\* at pci?** **brgphy\* at mii?** **gentbi\* at mii?** **nsgphy\* at mii?**

## DESCRIPTION

The **cas** driver provides support for various NICs based on the Sun Cassini/Cassini+ and National Semiconductor Saturn Ethernet controller chips, including the following:

- Sun GigaSwift Ethernet Adapter (10/100/1000baseT)

- Sun GigaSwift Ethernet MMF Adapter (1000baseSX)

- Sun Quad GigaSwift Ethernet UTP Adapter (10/100/1000baseT)

- Sun Quad GigaSwift PCI-X Adapter (10/100/1000baseT)

- Sun Dual Gigabit Ethernet and Dual SCSI/P Adapter (10/100/1000baseT)

It uses an internal or external PHY or an external 10-bit interface.

The **cas** driver supports several media types, which are selected via the [ifconfig(8)](/man/ifconfig/8.md) command. The supported media types are:

- **media** autoselect

  Attempt to autoselect the media type (default)

- **media** 1000baseT **mediaopt** full-duplex

  Use 1000baseT on copper, full duplex

- **media** 1000baseT **mediaopt** half-duplex

  Use 1000baseT on copper, half duplex

- **media** 1000baseSX **mediaopt** full-duplex

  Use 1000baseSX on fiber, full duplex

- **media** 1000baseSX **mediaopt** half-duplex

  Use 1000baseSX on fiber, half duplex

- **media** 100baseTX **mediaopt** full-duplex

  Use 100baseTX, full duplex

- **media** 100baseTX **mediaopt** half-duplex

  Use 100baseTX, half duplex

- **media** 10baseT **mediaopt** full-duplex

  Use 10baseT, full duplex

- **media** 10baseT **mediaopt** half-duplex

  Use 10baseT, half duplex

## SEE ALSO

[arp(4)](/man/arp/4.md), [brgphy(4)](/man/brgphy/4.md), [gentbi(4)](/man/gentbi/4.md), [ifmedia(4)](/man/ifmedia/4.md), [inet(4)](/man/inet/4.md), [intro(4)](/man/intro/4.md), [netintro(4)](/man/netintro/4.md), [nsgphy(4)](/man/nsgphy/4.md), [hostname.if(5)](/man/hostname.if/5.md), [ifconfig(8)](/man/ifconfig/8.md)

## HISTORY

OpenBSD support for **cas** first appeared in OpenBSD 4.1.

## AUTHORS

The **cas** driver was written by Mark Kettenis ⟨*kettenis@openbsd.org*⟩ based on the [gem(4)](/man/gem/4.md) driver.

## BUGS

The **cas** driver does not yet use many of the advanced features the Cassini chip offers.