Clean up the CPU/ChipSet interface, and get the PC8080 Video component ready to actually do something

modules/pcjs/lib/chipset.js

@@ -81,7 +81,7 @@ function ChipSet(parmsChipSet)
         Component.notice("Unrecognized ChipSet model: " + model);
     }
 
-    this.model = model && ChipSet.MODELS[model] || ChipSet.MODEL_5150_OTHER;
+    this.model = ChipSet.MODELS[model] || ChipSet.MODEL_5150_OTHER;
 
     var bSwitches;
     this.aDIPSwitches = [];
@@ -2126,6 +2126,36 @@ ChipSet.prototype.restore = function(data)
     return true;
 };
 
+/**
+ * start()
+ *
+ * Notification from the CPU that it's starting.
+ *
+ * @this {ChipSet}
+ */
+ChipSet.prototype.start = function()
+{
+    /*
+     * Currently, all we do with this notification is allow the speaker to make noise.
+     */
+    this.setSpeaker();
+};
+
+/**
+ * stop()
+ *
+ * Notification from the CPU that it's stopping.
+ *
+ * @this {ChipSet}
+ */
+ChipSet.prototype.stop = function()
+{
+    /*
+     * Currently, all we do with this notification is prevent the speaker from making noise.
+     */
+    this.setSpeaker();
+};
+
 ChipSet.aDMAControllerInit = [0, null, null, 0, new Array(4), 0];
 
 /**