Esp8266 erase flash.

After flashing to 512kb

 _____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v95 Copyright 2017 G.Williams
Espruino is Open Source. Our work is supported
only by sales of official boards and donations:
http://espruino.com/Donate
Flash map 512KB:256/256, manuf 0xe0 chip 0x4016
WARNING: *** Your flash chip does not match your flash map ***
>require("ESP8266").getFreeFlash();
=[
  { "addr": 487424, "length": 4096 }
 ]
> 

wifi.save() - works