Document long-form COM port device names on Windows, required to specify serial ports above 9
diff --git a/README b/README
index 680415c..faa0e14 100644
--- a/README
+++ b/README
@@ -212,7 +212,7 @@ FPGA mining boards(BitForce, Icarus) only options:
device depending on the version of udev being used.
On linux <arg> is usually of the format /dev/ttyUSBn
- On windows <arg> is usually of the format COMn
+ On windows <arg> is usually of the format \\.\COMn
(where n = the correct device number for the FPGA device)