---
name: "astro"
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/astro"
---

# astro(4)

Astro Memory and I/O controller

## NAME

**astro** – Astro Memory and I/O controller

## SYNOPSIS

**astro\* at mainbus?** **elroy\* at astro?**

## DESCRIPTION

The **astro** driver provides support for the Astro memory and I/O controller used on systems with PA-8500 and later 64-bit CPUs. It functions as a bridge from the Runway bus to up to 8 I/O ropes that connect to Elroy chips. Astro contains an IOMMU and provides support for cache coherent DMA.

## SEE ALSO

[cpu(4)](/cpu/4.md), [elroy(4)](/elroy/4.md), [intro(4)](/intro/4.md), [runway(4)](/runway/4.md)

## HISTORY

The **astro** driver first appeared in OpenBSD 4.2.