GPL Source code: http://support.wdc.com/product/download.asp?groupid=1701&sid=177&lang=en

Device Specific Terminology

On at least some WD N600 devices the ART-partition is named “radiocfg” in /proc/mtd. (knowing this could save you some time and/or allow proper pre-configuration backup.)

→ Install OpenWrt (generic explanation)

There are 3 installation methods. With newer versions of OpenWrt, it's likely only method 3 will work.

1) Download the factory image as shown above
2) Configure your computers IP address to 192.168.1.10 and connect to a LAN port in the router.
3) Turn the router off.
4) Using a paperclip, press and hold the reset button on the bottom of the router and turn it on. Hold the reset button for at least 15 seconds. Wait until the power light on the front is slowly flashing on and off.
5) On your computer, visit http://192.168.1.1 NOTE: You will not be able to ping this address.
6) Upload the factory image as downloaded earlier.
7) The router will now flash OpenWrt. This will take a couple of minutes to achieve. You can ping 192.168.1.1 and watch for ping replies to see when your router has rebooted into OpenWrt.

1) Visit the administration page on the router (http://192.168.x.x) and login.
2) Enter the following URL: http://192.168.x.x/telnet.php
3) Enable telnetd, click save.
4) Log in with username “Alphanetworks”, password “wrgnd16_wd_db600”
5) Use wget to copy in the *factory.bin file
6) Call fwupdater -i *factory.bin
7) Ignore the failure message at the end of the upgrade, just reboot
8) Enjoy!

1) Follow method 1, but instead of uploading OpenWrt use Gargoyle. Download gargoyle_1.9.0-ar71xx-generic-mynet-n600-squashfs-factory.bin from the Gargoyle downloads page.
2) Once Gargoyle is flashed and the router is rebooted, go to 192.168.1.1 and update the firmware with sysupgrade image as shown above.
3) After OpenWrt is finished flashing, log into the router by SSHing into root@192.168.1.1

Pictures
Top of mainboard:

Bottom of mainboard:
There seems to be a 5 x pin header and a 14 pin (not connected) test connector on the mainboard.

14 pin header:

Looking under the main 'can', the CPU is:
Atheros AR9344-BC2A PBT204.00B 1128 TAIWAN

Next to that, there's what looks to be 2 x RAM chips:
ESMT M14D5121632A ASH1 -2.58 P127W02 201

Under the second smaller 'can', I see another Atheros Chip:
Atheros AR9382-ALTA PFT676.00B 1203

The UART is accessable via JP1 (which already has a header connected!). You will need a TTL to RS232 (ie a MAX232 circuit) to utilise this. See picture further down. The pinout is:
[TxD] [GND] [3.3v] [RxD]
JP1

JP1 - UART serial header:

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