AMDMSR(4) | Device Drivers Manual (i386) | AMDMSR(4)

# NAME

`amdmsr` — access MSRs on certain AMD Geode LX systems

# SYNOPSIS

`amdmsr0 at mainbus?`

# DESCRIPTION

The `amdmsr` device provides access to the Model Specific Registers (MSRs) on systems with an AMD Geode LX CPU and graphics processor.

## IOCTL INTERFACE

MSRs can be read or written via `ioctl`() calls performed on /dev/amdmsr. Declarations and data types are to be found in `<machine/amdmsr.h>`.

Read or write requests are performed using:

    struct amdmsr_req {
    	u_int32_t addr;	/* 32-bit MSR address */
    	u_int64_t val;	/* 64-bit MSR value */
    };

The RDMSR ioctl is used to read an MSR register.

The WRMSR ioctl is used to write an MSR register.

# SEE ALSO

ioctl(2)

# HISTORY

`amdmsr` support was added in OpenBSD 4.4.

January 21, 2014 | Debian