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diff --git a/docs/user/Powersave.mdwn b/docs/user/Powersave.mdwn
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--- a/docs/user/Powersave.mdwn
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@@ -78,4 +78,14 @@ Savings highly depend on hardware. There are some numbers from my X61s:
 
 [Here](http://www.techarp.com/showarticle.aspx?artno=420&pgno=4) you can find more general info about devices' D-states.
 
+## AHCI
+
+Some AHCI host bus adapters have link power management support.
+This feature can be controlled with a per-port sysctl.
+
+     $ sysctl hw.ahci0
+     hw.ahci0.0.link_pwr_mgmt: 2
+
+Enabling AHCI link power management can save ~0.8W.
+
 *More to come ...*