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

# smu(4)

Apple System Management Unit

## NAME

**smu** – Apple System Management Unit

## SYNOPSIS

**smu? at mainbus0**

## DESCRIPTION

The **smu** driver provides support for the System Management Unit found on Apple iMac G5 and some Power Mac G5 machines.

The System Management Unit controls the fans in these systems. It also contains the real-time clock and an I2C controller.

## SEE ALSO

[iic(4)](/iic/4.md), [intro(4)](/intro/4.md)

## HISTORY

The **smu** driver first appeared in OpenBSD 3.9.

## AUTHORS

The **smu** driver was written by Mark Kettenis.

## BUGS

Fan control is not implemented yet.