diff --git a/src/gopheros/device/acpi/aml/vm_convert.go b/src/gopheros/device/acpi/aml/vm_convert.go
new file mode 100644
index 0000000..180133f
--- /dev/null
+++ b/src/gopheros/device/acpi/aml/vm_convert.go
@@ -0,0 +1,133 @@
+package aml
+
+// valueType represents the data types that the AML interpreter can process.
+type valueType uint8
+
+// The list of supporte AML value types (see p. 876 of ACPI 6.2 standard)
+const (
+	valueTypeUninitialized valueType = iota
+	valueTypeBuffer
+	valueTypeBufferField
+	valueTypeDDBHandle
+	valueTypeDebugObject
+	valueTypeDevice
+	valueTypeEvent
+	valueTypeFieldUnit
+	valueTypeInteger // we also treat constants as integers
+	valueTypeMethod
+	valueTypeMutex
+	valueTypeObjectRef
+	valueTypeRegion
+	valueTypePackage
+	valueTypeString
+	valueTypePowerResource
+	valueTypeProcessor
+	valueTypeRawDataBuffer
+	valueTypeThermalZone
+)
+
+// String implements fmt.Stringer for valueType.
+func (vt valueType) String() string {
+	switch vt {
+	case valueTypeBuffer:
+		return "Buffer"
+	case valueTypeBufferField:
+		return "BufferField"
+	case valueTypeDDBHandle:
+		return "DDBHandle"
+	case valueTypeDebugObject:
+		return "DebugObject"
+	case valueTypeDevice:
+		return "Device"
+	case valueTypeEvent:
+		return "Event"
+	case valueTypeFieldUnit:
+		return "FieldUnit"
+	case valueTypeInteger:
+		return "Integer"
+	case valueTypeMethod:
+		return "Method"
+	case valueTypeMutex:
+		return "Mutex"
+	case valueTypeObjectRef:
+		return "ObjectRef"
+	case valueTypeRegion:
+		return "Region"
+	case valueTypePackage:
+		return "Package"
+	case valueTypeString:
+		return "String"
+	case valueTypePowerResource:
+		return "PowerResource"
+	case valueTypeProcessor:
+		return "Processor"
+	case valueTypeRawDataBuffer:
+		return "RawDataBuffer"
+	case valueTypeThermalZone:
+		return "ThermalZone"
+	default:
+		return "Uninitialized"
+	}
+}
+
+// vmTypeOf returns the type of data stored inside the supplied argument.
+func vmTypeOf(ctx *execContext, arg interface{}) valueType {
+	// Some objects (e.g args, constEntity contents) may require to perform
+	// more than one pass to figure out their type
+	for {
+		switch typ := arg.(type) {
+		case *constEntity:
+			// check the value stored inside
+			arg = typ.val
+		case *Device:
+			return valueTypeDevice
+		case *Method:
+			return valueTypeMethod
+		case *bufferEntity:
+			return valueTypeBuffer
+		case *bufferFieldEntity:
+			return valueTypeBufferField
+		case *fieldUnitEntity, *indexFieldEntity:
+			return valueTypeFieldUnit
+		case *regionEntity:
+			return valueTypeRegion
+		case *objRef:
+			return valueTypeObjectRef
+		case *eventEntity:
+			return valueTypeEvent
+		case *mutexEntity:
+			return valueTypeMutex
+		case Entity:
+			op := typ.getOpcode()
+
+			switch op {
+			case opPackage:
+				return valueTypePackage
+			case opPowerRes:
+				return valueTypePowerResource
+			case opProcessor:
+				return valueTypeProcessor
+			case opThermalZone:
+				return valueTypeThermalZone
+			}
+
+			// Check if this a local or method arg; if so we need to
+			// fetch the arg and check its type
+			if op >= opLocal0 && op <= opLocal7 {
+				arg = ctx.localArg[op-opLocal0]
+			} else if op >= opArg0 && op <= opArg6 {
+				arg = ctx.methodArg[op-opArg0]
+			} else {
+				return valueTypeUninitialized
+			}
+		case string:
+			return valueTypeString
+		case uint64, bool:
+			return valueTypeInteger
+		case []byte:
+			return valueTypeRawDataBuffer
+		default:
+			return valueTypeUninitialized
+		}
+	}
+}
diff --git a/src/gopheros/device/acpi/aml/vm_convert_test.go b/src/gopheros/device/acpi/aml/vm_convert_test.go
new file mode 100644
index 0000000..446e9d6
--- /dev/null
+++ b/src/gopheros/device/acpi/aml/vm_convert_test.go
@@ -0,0 +1,174 @@
+package aml
+
+import (
+	"testing"
+)
+
+func TestValueTypeToString(t *testing.T) {
+	specs := map[valueType]string{
+		valueTypeBuffer:        "Buffer",
+		valueTypeBufferField:   "BufferField",
+		valueTypeDDBHandle:     "DDBHandle",
+		valueTypeDebugObject:   "DebugObject",
+		valueTypeDevice:        "Device",
+		valueTypeEvent:         "Event",
+		valueTypeFieldUnit:     "FieldUnit",
+		valueTypeInteger:       "Integer",
+		valueTypeMethod:        "Method",
+		valueTypeMutex:         "Mutex",
+		valueTypeObjectRef:     "ObjectRef",
+		valueTypeRegion:        "Region",
+		valueTypePackage:       "Package",
+		valueTypeString:        "String",
+		valueTypePowerResource: "PowerResource",
+		valueTypeProcessor:     "Processor",
+		valueTypeRawDataBuffer: "RawDataBuffer",
+		valueTypeThermalZone:   "ThermalZone",
+		valueTypeUninitialized: "Uninitialized",
+	}
+
+	for vt, exp := range specs {
+		if got := vt.String(); got != exp {
+			t.Errorf("expected valueType %d string representation to be %q; got %q", vt, exp, got)
+		}
+	}
+}
+
+func TestVMTypeOf(t *testing.T) {
+	specs := []struct {
+		ctx     *execContext
+		in      interface{}
+		expType valueType
+	}{
+		{
+			nil,
+			&constEntity{val: uint64(42)},
+			valueTypeInteger,
+		},
+		{
+			nil,
+			&constEntity{val: "some string"},
+			valueTypeString,
+		},
+		{
+			nil,
+			&Device{},
+			valueTypeDevice,
+		},
+		{
+			nil,
+			&Method{},
+			valueTypeMethod,
+		},
+		{
+			nil,
+			&bufferEntity{},
+			valueTypeBuffer,
+		},
+		{
+			nil,
+			&bufferFieldEntity{},
+			valueTypeBufferField,
+		},
+		{
+			nil,
+			&fieldUnitEntity{},
+			valueTypeFieldUnit,
+		},
+		{
+			nil,
+			&indexFieldEntity{},
+			valueTypeFieldUnit,
+		},
+		{
+			nil,
+			&regionEntity{},
+			valueTypeRegion,
+		},
+		{
+			nil,
+			&objRef{},
+			valueTypeObjectRef,
+		},
+		{
+			nil,
+			&eventEntity{},
+			valueTypeEvent,
+		},
+		{
+			nil,
+			&mutexEntity{},
+			valueTypeMutex,
+		},
+		{
+			nil,
+			&unnamedEntity{op: opPackage},
+			valueTypePackage,
+		},
+		{
+			nil,
+			&unnamedEntity{op: opPowerRes},
+			valueTypePowerResource,
+		},
+		{
+			nil,
+			&unnamedEntity{op: opProcessor},
+			valueTypeProcessor,
+		},
+		{
+			nil,
+			&unnamedEntity{op: opThermalZone},
+			valueTypeThermalZone,
+		},
+		{
+			&execContext{
+				localArg: [maxLocalArgs]interface{}{
+					uint64(42),
+				},
+			},
+			&unnamedEntity{op: opLocal0},
+			valueTypeInteger,
+		},
+		{
+			&execContext{
+				methodArg: [maxMethodArgs]interface{}{
+					uint64(42),
+					"foo",
+				},
+			},
+			&unnamedEntity{op: opArg1},
+			valueTypeString,
+		},
+		{
+			nil,
+			"foo",
+			valueTypeString,
+		},
+		{
+			nil,
+			uint64(42),
+			valueTypeInteger,
+		},
+		{
+			nil,
+			[]byte("some data"),
+			valueTypeRawDataBuffer,
+		},
+		{
+			nil,
+			&unnamedEntity{op: opAdd},
+			valueTypeUninitialized,
+		},
+		{
+			nil,
+			int64(0xbadf00d),
+			valueTypeUninitialized,
+		},
+	}
+
+	for specIndex, spec := range specs {
+		if got := vmTypeOf(spec.ctx, spec.in); got != spec.expType {
+			t.Errorf("[spec %d] expected to get value type %s; got %s", specIndex, spec.expType, got)
+		}
+	}
+}