Update README.md

README.md

@@ -8,6 +8,9 @@ Tested and working also for **T580**!
 ### Undervolt:
 The script now also supports **undervolting** the CPU by configuring voltage offsets for CPU, cache, GPU, System Agent and Analog I/O planes. The script will re-apply undervolt on resume from standby and hibernate by listening to DBus signals.
 
+### HWP override (EXPERIMENTAL):
+I have found that under load my CPU was not always hitting max turbo frequency, in particular when using one/two cores only. For instance, running [prime95](https://www.mersenne.org/download/) (1 core, test #1) my CPU is limited to about 3500 MHz over the theoretical 4000 MHz maximum. The reason is the value for the HWP energy performance [hints](http://manpages.ubuntu.com/manpages/artful/man8/x86_energy_perf_policy.8.html). By default TLP sets this value to "balance_performance" on AC in order to reduce the power consumption/heat in idle. By setting this value to "performance" I was able to reach 3900 MHz in the prime95 single core test, achieving a +400 MHz boost. Since this value forces the CPU to full speed even during idle, a new experimental feature allows to automatically set HWP to performance under load and revert it to balanced when idle. This feature can be enabled (in AC mode *only*) by setting to `True` the `HWP_Mode` parameter in the config file. 
+
 ## Requirements
 The python module `python-periphery` is used for accessing the MCHBAR register by memory mapped I/O. You also need `dbus` and `gobject` python bindings for listening to dbus signals on resume from sleep/hibernate.