From DD-WRT Wiki
This page applies to version 1. For version 2, see Linksys E1200v2
 Hardware Information
|CPU Speed||300 MHz|
|Flash ROM||4 MB|
|WLAN Max Speed||300 mbps|
|Switch||4x 10/100 LAN + 1 10/100 WAN|
 Flashing Instructions
After using the trailed build file for the initial flash (yes the file with the router name in it) only use nv64k builds to upgrade with or you will brick your unit. Don't confuse this unit with some of the other Linksys E-Series units that use nv60k builds, this one uses nv64k builds!
- Read the Peacock Announcement carefully.
- Disconnect all cables and wireless clients.
- Do a 30/30/30 reset on router
- Connect 1 Lan cable to pc doing the flash.
- Log into Linkysys Web Interface Firmware Upgrade page at 192.168.1.1 and flash the firmware E1200 Trailed Initial Flash Build
- Wait 5 minutes to assure flash integrity.
- Power cycle by unplugging the E1200 for 5 seconds.
- Plug the E1200 back in and wait about 2 minutes until it finishes booting.
- Do a 30/30/30 reset on router.
- Wait 3 minutes and log into web interface.
- You are done.
- Due to this unit only having a 4MB flash, you can only use nv64k builds that fit a 4MB flash footprint, using any bigger builds to upgrade with can either fail or worse, brick your unit. You been warned!
 Build Information
As noted in bold at the beginning of the flashing instructions, only use builds with nv64k in the name for upgrading - otherwise follow the initial flash instructions above if you are going from stock to dd-wrt, any other builds for upgrading an existing dd-wrt install without nv64k in the name will brick your router! This unit was supported with build 18946 or greater, this means you cannot use a build with a number lesser than 18946. For the safest results, use builds that are linked within this wiki as they have most likely been forum tested with ok reported results.
To find the latest builds, you can browse the DD-WRT file server and look for the broadcom_K26 folder, in there is the appropriate for your unit. Be aware that these are beta test builds and should be used with caution!
 More Information
Good build for this device is 21676 big.
Forum thread: http://www.dd-wrt.com/phpBB2/viewtopic.php?t=153302
 Reverting to Stock Firmware
It has been asked about: "how do i revert back to stock firmware?" and the answer is download the stock firmware image from the manufacturer's website, reset the router back to defaults using a 30-30-30 hard reset, then flash the stock image from within the dd-wrt webgui. After 5 minutes it should finish, you will then need to do another 30-30-30 reset and then access the stock webgui @ 192.168.1.1