diff --git a/src/main/java/li/cil/oc/api/machine/Architecture.java b/src/main/java/li/cil/oc/api/machine/Architecture.java
index 43a9c8f9a..ff26e6286 100644
--- a/src/main/java/li/cil/oc/api/machine/Architecture.java
+++ b/src/main/java/li/cil/oc/api/machine/Architecture.java
@@ -2,6 +2,11 @@ package li.cil.oc.api.machine;
 
 import net.minecraft.nbt.NBTTagCompound;
 
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
 /**
  * This interface abstracts away any language specific details for the Machine.
  * <p/>
@@ -11,12 +16,6 @@ import net.minecraft.nbt.NBTTagCompound;
  * Java Lua architecture (using LuaJ).
  */
 public interface Architecture {
-    /**
-     * A display friendly name of the architecture, mainly intended to be used
-     * when iterating all {@link li.cil.oc.api.Machine#architectures()}.
-     */
-    String name();
-
     /**
      * Used to check if the machine is fully initialized. If this is false no
      * signals for detected components will be generated. Avoids duplicate
@@ -133,4 +132,16 @@ public interface Architecture {
      * @param nbt the tag compound to save to.
      */
     void save(NBTTagCompound nbt);
+
+    /**
+     * Architectures can be annotated with this to provide a nice display name.
+     * <p/>
+     * This is used when the name of an architecture has to be displayed to the
+     * user, such as when cycling architectures on a CPU.
+     */
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target(ElementType.TYPE)
+    static @interface Name {
+        String value();
+    }
 }
diff --git a/src/main/resources/assets/opencomputers/lang/de_DE.lang b/src/main/resources/assets/opencomputers/lang/de_DE.lang
index 76f5d5e17..d3275d568 100644
--- a/src/main/resources/assets/opencomputers/lang/de_DE.lang
+++ b/src/main/resources/assets/opencomputers/lang/de_DE.lang
@@ -195,6 +195,7 @@ oc:tooltip.CircuitBoard=Mühsam ernährt sich das Eichhörnchen. Wenn es groß w
 oc:tooltip.ControlUnit=Klingt wichtig, ist es auch. Man baut daraus immerhin CPUs. Wie könnte es da nicht wichtig sein.
 oc:tooltip.ComponentBus=Diese Erweiterung erlaubt es es Servern, mit noch mehr Komponenten gleichzeitig zu kommunizieren, ähnlich wie CPUs.[nl] Supported components: §f%s§7.
 oc:tooltip.CPU=Kernstück eines jeden Computers. Die Taktrate hat einen leichten Schatten, aber was kann man von einer Taschensonnenuhr schon erwarten?[nl] Unterstützte Komponenten: §f%s§7.
+oc:tooltip.CPU.Architecture=Architektur: §f%s§7
 oc:tooltip.CuttingWire=Wird gebraucht, um Tonblöcke in Leiterplattenform zu bekommen. Vermutlich das ineffizienteste Werkzeug in der Geschichte der Menschheit, da es nach einer Verwendung kaputt geht.
 oc:tooltip.DebugCard=Kreativ-Modus-Gegenstand, erlaubt es die Welt zu manipulieren um das Testen zu erleichtern. Verwendung auf eigene Gefahr.
 oc:tooltip.Disassembler=Zerlegt Gegenstände in ihre Einzelteile. §lWarnung§7: zurückgewonnene Gegenstände haben eine %s%%-ige Chance beim Extrahieren kaputt zu gehen!
diff --git a/src/main/resources/assets/opencomputers/lang/en_US.lang b/src/main/resources/assets/opencomputers/lang/en_US.lang
index 682b19743..6d0000d0b 100644
--- a/src/main/resources/assets/opencomputers/lang/en_US.lang
+++ b/src/main/resources/assets/opencomputers/lang/en_US.lang
@@ -195,6 +195,7 @@ oc:tooltip.CircuitBoard=Now we're getting somewhere. Can be etched to obtain a p
 oc:tooltip.ControlUnit=This is the unit that... controls... stuff. You need it to build a CPU. So yeah, totally important.
 oc:tooltip.ComponentBus=This expansion allows servers to communicate with more components at the same time, similar to how CPUs do.[nl] Supported components: §f%s§7.
 oc:tooltip.CPU=An essential component of all computers. The clock rate is a bit unreliable, but what do you expect when it runs on a pocket sundial?[nl] Supported components: §f%s§7.
+oc:tooltip.CPU.Architecture=Architecture: §f%s§7
 oc:tooltip.CuttingWire=Used to cut clay blocks into circuit board shape. Breaks after one use, which probably makes it the most inefficient tool ever.
 oc:tooltip.DebugCard=Creative mode item, allows manipulating the world to make testing easier. Use at your own peril.
 oc:tooltip.Disassembler=Separates items into their original components. §lWarning§7: returned items have a %s%% chance of breaking in the process!
diff --git a/src/main/resources/assets/opencomputers/lua/kernel.lua b/src/main/resources/assets/opencomputers/lua/kernel.lua
index 2abcd0708..a69328c66 100644
--- a/src/main/resources/assets/opencomputers/lua/kernel.lua
+++ b/src/main/resources/assets/opencomputers/lua/kernel.lua
@@ -480,12 +480,13 @@ local function isDirect(address, method)
     return cachedValue
   end
   local methods, reason = spcall(component.methods, address)
-  if methods then
-    for name, info in pairs(methods) do
-      if name == method then
-        directCache[cacheKey] = info.direct
-        return info.direct
-      end
+  if not methods then
+    return false
+  end
+  for name, info in pairs(methods) do
+    if name == method then
+      directCache[cacheKey] = info.direct
+      return info.direct
     end
   end
   error("no such method", 1)
diff --git a/src/main/scala/li/cil/oc/common/Proxy.scala b/src/main/scala/li/cil/oc/common/Proxy.scala
index 3dff993d9..f8afd38c6 100644
--- a/src/main/scala/li/cil/oc/common/Proxy.scala
+++ b/src/main/scala/li/cil/oc/common/Proxy.scala
@@ -62,6 +62,7 @@ class Proxy {
     api.Machine.LuaArchitecture =
       if (LuaStateFactory.isAvailable && !Settings.get.forceLuaJ) classOf[NativeLuaArchitecture]
       else classOf[LuaJLuaArchitecture]
+    api.Machine.add(api.Machine.LuaArchitecture)
     api.Network.instance = network.Network
 
     if (Mods.ForgeMultipart.isAvailable) {
diff --git a/src/main/scala/li/cil/oc/common/item/CPU.scala b/src/main/scala/li/cil/oc/common/item/CPU.scala
index 03ab77e72..525866d37 100644
--- a/src/main/scala/li/cil/oc/common/item/CPU.scala
+++ b/src/main/scala/li/cil/oc/common/item/CPU.scala
@@ -1,6 +1,19 @@
 package li.cil.oc.common.item
 
+import java.util
+
 import li.cil.oc.Settings
+import li.cil.oc.api
+import li.cil.oc.api.machine.Architecture
+import li.cil.oc.util.Tooltip
+import net.minecraft.entity.player.EntityPlayer
+import net.minecraft.item.ItemStack
+import net.minecraft.nbt.NBTTagCompound
+import net.minecraft.util.ChatComponentTranslation
+import net.minecraft.world.World
+
+import scala.collection.convert.WrapAsScala._
+import scala.language.existentials
 
 class CPU(val parent: Delegator, val tier: Int) extends Delegate with ItemTier {
   override val unlocalizedName = super.unlocalizedName + tier
@@ -8,4 +21,49 @@ class CPU(val parent: Delegator, val tier: Int) extends Delegate with ItemTier {
   override protected def tooltipName = Option(super.unlocalizedName)
 
   override protected def tooltipData = Seq(Settings.get.cpuComponentSupport(tier))
+
+  override protected def tooltipExtended(stack: ItemStack, tooltip: util.List[String]) {
+    (if (stack.hasTagCompound) {
+      Option(stack.getTagCompound.getString(Settings.namespace + "archName"))
+    }
+    else {
+      val architectures = allArchitectures
+      architectures.headOption.map(_._2)
+    }) match {
+      case Some(archName) => tooltip.addAll(Tooltip.get("CPU.Architecture", archName))
+      case _ => // No architecture.
+    }
+  }
+
+  override def onItemRightClick(stack: ItemStack, world: World, player: EntityPlayer) = {
+    if (player.isSneaking) {
+      if (!world.isRemote) {
+        val architectures = allArchitectures
+        if (architectures.length > 0) {
+          val currentIndex = if (stack.hasTagCompound) {
+            val currentArch = stack.getTagCompound.getString(Settings.namespace + "archClass")
+            architectures.indexWhere(_._1.getName == currentArch)
+          }
+          else {
+            stack.setTagCompound(new NBTTagCompound())
+            -1
+          }
+          val index = (currentIndex + 1) % architectures.length
+          val (archClass, archName) = architectures(index)
+          stack.getTagCompound.setString(Settings.namespace + "archClass", archClass.getName)
+          stack.getTagCompound.setString(Settings.namespace + "archName", archName)
+          player.addChatMessage(new ChatComponentTranslation(Settings.namespace + "tooltip.CPU.Architecture", archName))
+        }
+        player.swingItem()
+      }
+    }
+    stack
+  }
+
+  private def allArchitectures = api.Machine.architectures.map { arch =>
+    arch.getAnnotation(classOf[Architecture.Name]) match {
+      case annotation: Architecture.Name => (arch, annotation.value)
+      case _ => (arch, arch.getSimpleName)
+    }
+  }.toArray
 }
diff --git a/src/main/scala/li/cil/oc/server/driver/item/CPU.scala b/src/main/scala/li/cil/oc/server/driver/item/CPU.scala
index 8f80afc17..e923dd217 100644
--- a/src/main/scala/li/cil/oc/server/driver/item/CPU.scala
+++ b/src/main/scala/li/cil/oc/server/driver/item/CPU.scala
@@ -1,15 +1,18 @@
 package li.cil.oc.server.driver.item
 
+import li.cil.oc.OpenComputers
 import li.cil.oc.Settings
 import li.cil.oc.api
-import li.cil.oc.api.Machine
 import li.cil.oc.api.driver.EnvironmentHost
 import li.cil.oc.api.driver.item.Processor
+import li.cil.oc.api.machine.Architecture
 import li.cil.oc.common.Slot
 import li.cil.oc.common.init.Items
 import li.cil.oc.common.item
 import net.minecraft.item.ItemStack
 
+import scala.collection.convert.WrapAsScala._
+
 object CPU extends Item with Processor {
   override def worksWith(stack: ItemStack) =
     isOneOf(stack, api.Items.get("cpu1"), api.Items.get("cpu2"), api.Items.get("cpu3"))
@@ -30,5 +33,15 @@ object CPU extends Item with Processor {
       case _ => 0
     }
 
-  override def architecture(stack: ItemStack) = Machine.LuaArchitecture
+  override def architecture(stack: ItemStack) = {
+    if (stack.hasTagCompound) {
+      val archClass = stack.getTagCompound.getString(Settings.namespace + "archClass")
+      try Class.forName(archClass).asSubclass(classOf[Architecture]) catch {
+        case t: Throwable =>
+          OpenComputers.log.warn("Failed getting class for CPU architecture.", t)
+          null
+      }
+    }
+    else api.Machine.architectures.headOption.orNull
+  }
 }
diff --git a/src/main/scala/li/cil/oc/server/machine/Machine.scala b/src/main/scala/li/cil/oc/server/machine/Machine.scala
index eedd27b04..02abce1bd 100644
--- a/src/main/scala/li/cil/oc/server/machine/Machine.scala
+++ b/src/main/scala/li/cil/oc/server/machine/Machine.scala
@@ -58,6 +58,9 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
 
   @volatile private var callBudget = 0.0
 
+  // We want to ignore the call limit in synchronized calls to avoid errors.
+  private var inSynchronizedCall = false
+
   // ----------------------------------------------------------------------- //
 
   var worldTime = 0L // Game-world time for os.time().
@@ -268,7 +271,7 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
     case _ => throw new NoSuchMethodException()
   }
 
-  private def checkLimit(limit: Int) {
+  private def checkLimit(limit: Int): Unit = if (!inSynchronizedCall) {
     val callCost = math.max(1.0 / limit, 0.001)
     if (callCost >= callBudget) {
       throw new LimitReachedException()
@@ -421,16 +424,13 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
         }
       // Perform a synchronized call (message sending).
       case Machine.State.SynchronizedCall =>
-        // Reset direct call budget again, just to be on the safe side...
-        // Theoretically it'd be possible for the executor to do some direct
-        // calls between the clear and the state check, which could in turn
-        // make this synchronized call fail due the limit still being maxed.
-        callBudget = maxCallBudget
         // We switch into running state, since we'll behave as though the call
         // were performed from our executor thread.
         switchTo(Machine.State.Running)
         try {
+          inSynchronizedCall = true
           architecture.runSynchronized()
+          inSynchronizedCall = false
           // Check if the callback called pause() or stop().
           state.top match {
             case Machine.State.Running =>
@@ -451,6 +451,9 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
             OpenComputers.log.warn("Faulty architecture implementation for synchronized calls.", e)
             crash("gui.Error.InternalError")
         }
+        finally {
+          inSynchronizedCall = false
+        }
 
         assert(state.top != Machine.State.Running)
       case _ => // Nothing special to do, just avoid match errors.
@@ -871,7 +874,8 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
 }
 
 object Machine extends MachineAPI {
-  val checked = mutable.Set.empty[Class[_ <: Architecture]]
+  // Keep registration order, to allow deterministic iteration of the architectures.
+  val checked = mutable.LinkedHashSet.empty[Class[_ <: Architecture]]
 
   override def add(architecture: Class[_ <: Architecture]) {
     if (!checked.contains(architecture)) {
@@ -885,7 +889,7 @@ object Machine extends MachineAPI {
     }
   }
 
-  override def architectures() = scala.collection.convert.WrapAsJava.asJavaIterable(checked)
+  override def architectures = scala.collection.convert.WrapAsJava.asJavaIterable(checked)
 
   override def create(host: MachineHost) = new Machine(host)
 
diff --git a/src/main/scala/li/cil/oc/server/machine/luac/NativeLuaArchitecture.scala b/src/main/scala/li/cil/oc/server/machine/luac/NativeLuaArchitecture.scala
index 66bc22b04..5d246ca2f 100644
--- a/src/main/scala/li/cil/oc/server/machine/luac/NativeLuaArchitecture.scala
+++ b/src/main/scala/li/cil/oc/server/machine/luac/NativeLuaArchitecture.scala
@@ -4,6 +4,9 @@ import java.io.FileNotFoundException
 import java.io.IOException
 
 import com.google.common.base.Strings
+import li.cil.oc.OpenComputers
+import li.cil.oc.Settings
+import li.cil.oc.api
 import li.cil.oc.api.machine.Architecture
 import li.cil.oc.api.machine.ExecutionResult
 import li.cil.oc.api.machine.LimitReachedException
@@ -11,12 +14,10 @@ import li.cil.oc.common.SaveHandler
 import li.cil.oc.server.machine.Machine
 import li.cil.oc.util.ExtendedLuaState.extendLuaState
 import li.cil.oc.util.LuaStateFactory
-import li.cil.oc.OpenComputers
-import li.cil.oc.Settings
-import li.cil.oc.api
 import li.cil.repack.com.naef.jnlua._
 import net.minecraft.nbt.NBTTagCompound
 
+@Architecture.Name("Lua")
 class NativeLuaArchitecture(val machine: api.machine.Machine) extends Architecture {
   private[machine] var lua: LuaState = null
 
@@ -127,8 +128,6 @@ class NativeLuaArchitecture(val machine: api.machine.Machine) extends Architectu
 
   // ----------------------------------------------------------------------- //
 
-  override def name() = "Lua"
-
   override def isInitialized = kernelMemory > 0
 
   override def recomputeMemory() = Option(lua) match {
diff --git a/src/main/scala/li/cil/oc/server/machine/luaj/LuaJLuaArchitecture.scala b/src/main/scala/li/cil/oc/server/machine/luaj/LuaJLuaArchitecture.scala
index beeed8d38..ee6a5e77d 100644
--- a/src/main/scala/li/cil/oc/server/machine/luaj/LuaJLuaArchitecture.scala
+++ b/src/main/scala/li/cil/oc/server/machine/luaj/LuaJLuaArchitecture.scala
@@ -4,19 +4,20 @@ import java.io.FileNotFoundException
 import java.io.IOException
 
 import com.google.common.base.Strings
+import li.cil.oc.OpenComputers
+import li.cil.oc.Settings
+import li.cil.oc.api
 import li.cil.oc.api.machine.Architecture
 import li.cil.oc.api.machine.ExecutionResult
 import li.cil.oc.api.machine.LimitReachedException
 import li.cil.oc.server.machine.Machine
 import li.cil.oc.util.ScalaClosure
 import li.cil.oc.util.ScalaClosure._
-import li.cil.oc.OpenComputers
-import li.cil.oc.Settings
-import li.cil.oc.api
 import li.cil.repack.org.luaj.vm2._
 import li.cil.repack.org.luaj.vm2.lib.jse.JsePlatform
 import net.minecraft.nbt.NBTTagCompound
 
+@Architecture.Name("LuaJ")
 class LuaJLuaArchitecture(val machine: api.machine.Machine) extends Architecture {
   private[machine] var lua: Globals = _
 
@@ -90,8 +91,6 @@ class LuaJLuaArchitecture(val machine: api.machine.Machine) extends Architecture
 
   // ----------------------------------------------------------------------- //
 
-  override def name() = "LuaJ"
-
   override def isInitialized = doneWithInitRun
 
   override def recomputeMemory() = memory = machine.host.installedMemory