diff --git a/pid/pidloop.cpp b/pid/pidloop.cpp
new file mode 100644
index 0000000..b684747
--- /dev/null
+++ b/pid/pidloop.cpp
@@ -0,0 +1,117 @@
+/**
+ * Copyright 2017 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "pidloop.hpp"
+
+#include "pid/pidcontroller.hpp"
+#include "pid/tuning.hpp"
+#include "sensors/sensor.hpp"
+
+#include <boost/asio/steady_timer.hpp>
+#include <chrono>
+#include <map>
+#include <memory>
+#include <thread>
+#include <vector>
+
+static void processThermals(PIDZone* zone)
+{
+    // Get the latest margins.
+    zone->updateSensors();
+    // Zero out the RPM set point goals.
+    zone->clearRPMSetPoints();
+    zone->clearRPMCeilings();
+    // Run the margin PIDs.
+    zone->processThermals();
+    // Get the maximum RPM setpoint.
+    zone->determineMaxRPMRequest();
+}
+
+void pidControlLoop(PIDZone* zone, boost::asio::steady_timer& timer, bool first,
+                    int ms100cnt)
+{
+    if (first)
+    {
+        if (tuningLoggingEnabled)
+        {
+            zone->initializeLog();
+        }
+
+        zone->initializeCache();
+        processThermals(zone);
+    }
+
+    timer.expires_after(std::chrono::milliseconds(100));
+    timer.async_wait(
+        [zone, &timer, ms100cnt](const boost::system::error_code& ec) mutable {
+            /*
+             * This should sleep on the conditional wait for the listen thread
+             * to tell us it's in sync.  But then we also need a timeout option
+             * in case phosphor-hwmon is down, we can go into some weird failure
+             * more.
+             *
+             * Another approach would be to start all sensors in worst-case
+             * values, and fail-safe mode and then clear out of fail-safe mode
+             * once we start getting values.  Which I think it is a solid
+             * approach.
+             *
+             * For now this runs before it necessarily has any sensor values.
+             * For the host sensors they start out in fail-safe mode.  For the
+             * fans, they start out as 0 as input and then are adjusted once
+             * they have values.
+             *
+             * If a fan has failed, it's value will be whatever we're told or
+             * however we retrieve it.  This program disregards fan values of 0,
+             * so any code providing a fan speed can set to 0 on failure and
+             * that fan value will be effectively ignored.  The PID algorithm
+             * will be unhappy but nothing bad will happen.
+             *
+             * TODO(venture): If the fan value is 0 should that loop just be
+             * skipped? Right now, a 0 value is ignored in
+             * FanController::inputProc()
+             */
+
+            // Check if we should just go back to sleep.
+            if (zone->getManualMode())
+            {
+                pidControlLoop(zone, timer, false, ms100cnt);
+                return;
+            }
+
+            // Get the latest fan speeds.
+            zone->updateFanTelemetry();
+
+            if (10 <= ms100cnt)
+            {
+                ms100cnt = 0;
+
+                processThermals(zone);
+            }
+
+            // Run the fan PIDs every iteration.
+            zone->processFans();
+
+            if (tuningLoggingEnabled)
+            {
+                zone->getLogHandle() << "," << zone->getFailSafeMode();
+                zone->getLogHandle() << std::endl;
+            }
+
+            ms100cnt += 1;
+
+            pidControlLoop(zone, timer, false, ms100cnt);
+        });
+}