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

# viasio(4)

VIA VT1211 LPC Super I/O

## NAME

**viasio** – VIA VT1211 LPC Super I/O

## SYNOPSIS

**viasio\* at isa? port 0x2e flags 0x0000** **viasio\* at isa? port 0x4e flags 0x0000**

## DESCRIPTION

The **viasio** driver provides support for the VIA VT1211 LPC Super I/O IC. The hardware monitoring and watchdog timer functions are currently supported.

The hardware monitor provides hardware monitoring capabilities to be used with the [sysctl(8)](/sysctl/8.md) interface. The following monitoring sensors are available:

| | | |
| --- | --- | --- |
| **Sensor** | **Units** | **Typical use** |
| TEMP1 | uK | Pentium II type thermal diode |
| UCH1 | uK or uV DC | CPU temperature |
| UCH2 | uK or uV DC | System temperature |
| UCH3 | uK or uV DC | CPU core voltage |
| UCH4 | uK or uV DC | +5V |
| UCH5 | uK or uV DC | +12V |
| +3.3V | uV | Internal +3.3V |
| FAN1 | RPM | Fan tachometer |
| FAN2 | RPM | Fan tachometer |

If the hardware monitor is not enabled by firmware, the driver can try to enable it if value 0x0001 is present in the *flags*. Note that enabling the hardware monitor can lead to unexpected results.

The watchdog timer provides a standard [watchdog(4)](/watchdog/4.md) interface. If the watchdog timer is not enabled by firmware, the driver can try to enable it if value 0x0002 is present in the *flags*.

## SEE ALSO

[intro(4)](/intro/4.md), [isa(4)](/isa/4.md), [watchdog(4)](/watchdog/4.md), [sensorsd(8)](/sensorsd/8.md), [sysctl(8)](/sysctl/8.md)

## HISTORY

The **viasio** driver first appeared in OpenBSD 3.8.

## AUTHORS

The **viasio** driver was written by Alexander Yurchenko ⟨*grange@openbsd.org*⟩.