Difference between firmwares esp8266_4mb and esp8266 ?

It was 16kb of minified code I uploaded and tried to save.

This is the output I get from the "4mb combined", 1700 blocks and no graphics:

_____                 _
|   __|___ ___ ___ _ _|_|___ ___
|   __|_ -| . |  _| | | |   | . |
|_____|___|  _|_| |___|_|_|_|___|
          |_| http://espruino.com
 1v95.20 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 4MB:1024/1024, manuf 0xc8 chip 0x4016
>process.memory()
={ "free": 1677, "usage": 23, "total": 1700, "history": 0,
  "gc": 0, "gctime": 1.352 }
>require("ESP8266").getState();
={
  "sdkVersion": "2.0.0(5a875ba)",
  "cpuFrequency": 160, "freeHeap": 9728, "maxCon": 10,
  "flashMap": "4MB:1024/1024",
  "flashKB": 4096,
  "flashChip": "0xc8 0x4016"
 }
>Graphics
Uncaught ReferenceError: "Graphics" is not defined
>require("Flash").getFree()
=[
  { "addr": 2097152, "length": 1048576 },
  { "addr": 3145728, "length": 262144 },
  { "addr": 3407872, "length": 262144 },
  { "addr": 3670016, "length": 262144 },
  { "addr": 3932160, "length": 262144 }
 ]