---
name: "mcbus"
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/mcbus"
---

# mcbus(4)

MCBUS system bus

## NAME

**mcbus**, **mcmem** – MCBUS system bus

## SYNOPSIS

**mcbus\* at mainbus0** **mcmem\* at mcbus? mid ?**

## DESCRIPTION

The **mcbus** driver provides support for the MCBUS system bus found on AlphaServer 4100 and 1200 systems.

The following devices are supported by the **mcbus** driver:

- mcmem

  memory modules attached to the MCBUS main system bus.

- mcpcia

  MCPCIA MCBUS-to-PCI bus adapter

## SEE ALSO

[intro(4)](/intro/4.md), [mainbus(4)](/mainbus/4.md), [mcpcia(4)](/mcpcia/4.md)

## BUGS

Only one MCBUS bus can exist within the system.