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+# Intel Power Gadget
+
+[Intel Power Gadget](https://software.intel.com/en-us/articles/intel-power-gadget/)
+provides real-time graphs of various power-related measures and
+estimates, all taken from the Intel RAPL MSRs. This article provides a
+basic introduction.
+
+**Note**: The [power profiling
+overview](power_profiling_overview.md) is
+worth reading at this point if you haven\'t already. It may make parts
+of this document easier to understand.
+
+The main strengths of this tool are (a) it works on Windows, unlike most
+other power-related tools, and (b) it shows this data in graph form,
+which is occasionally useful. On Mac and Linux, `tools/power/rapl`
+[](tools_power_rapl.md) is probably a better tool
+to use.
+
+## Understanding the Power Gadget output
+
+The following screenshot (from the Mac version) demonstrates the
+available measurements.
+
+![](https://mdn.mozillademos.org/files/11365/Intel-Power-Gadget.png)
+
+The three panes display the following information:
+
+-   **Power**: Shows power estimates for the package and the cores
+    (\"IA\"). These are reasonably useful for power profiling purposes,
+    but Mozilla\'s `rapl` utility provides these along with GPU and RAM
+    estimates, and in a command-line format that is often easier to use.
+-   **Frequency**: Shows operating frequency measurements for the cores
+    (\"IA\") and the GPU (\"GT\"). These measurements aren\'t
+    particularly useful for power profiling purposes.
+-   **Temperature**: Shows the package temperature. This is interesting,
+    but again not useful for power profiling purposes. Specifically,
+    the temperature is a proxy measurement that is *affected by*
+    processor power consumption, rather than one that *affects* it,
+    which makes it even less useful than most proxy measurements.
+
+Intel Power Gadget can also log these results to a file. This feature
+has been used in [energia](https://github.com/mozilla/energia), Roberto
+Vitillo\'s tool for systematically measuring differential power usage
+between different browsers. (An energia dashboard can be seen
+[here](http://people.mozilla.org/~rvitillo/dashboard/); please note that
+the data has not been updated since early 2014.)
+
+Version 3.0 (available on Mac and Windows, but not on Linux) also
+exposes an API from which the same measurements can be extracted
+programmatically. At one point the Gecko Profiler [used this
+API](https://benoitgirard.wordpress.com/2012/06/29/correlating-power-usage-with-performance-data-using-the-gecko-profiler-and-intel-sandy-bridge/)
+on Windows to implement experimental package power estimates.
+Unfortunately, the Gecko profiler takes 1000 samples per second on
+desktop and is CPU intensive and so is likely to skew the RAPL estimates
+significantly, so the API integration was removed. The API is otherwise
+unlikely to be of interest to Mozilla developers.