WARNING: THIS IS ONLY FOR TPLINK AR7240/AR7241 DEVICES, **NOT** AR9331, AR9341, ETC !!!
Hi, I did the same thing (flash upgrade to 8M).
Did you know that ar7240 can run at 400MHZ right?
I found an uboot in a chinese forum that works with my wr740n v2, modded to use 8MB flash, and...also overclocking abilities!!
The maximum stable frequency for me is 430MHz (DDR goes up to 430MHZ too).
At 440MHz it worked but the LAN did not longer work in the uboot or openwrt. But I was able to boot at even 480MHz! sadly...no LAN so stuck at 430MHz.
Remember that no LAN = no way to transfer data to the router = no way to recover = BRICKED!!.
From 350 to 430MHz, it went from 235 Bogomips, to 286!
How to overclock:
Open the modded uboot with an Hex editor, go to address 0x1FD00.
The uboot is modded, it has 4 OC profiles. Any of them can be enabled by setting to "1" an hex value.
The last byte of each profile is the multiplier. DON'T CHANGE THE "08" !!
If you saw the bootlog, it says "Ref:5MHz".
So, we have to use a multiplier in base of that speed to get the AHB clock speed.
In the way it works, the DDR and CPU speed is the double of the AHB.
Example: 40 multiplier.
AHB speed: 40*5= 200MHz.
CPU and DDR will be 200*2=400MHz
Remember that the bin file works in hexadecimal!! decimal 40 = 28 hex !
Here a nice pic I made for better explanation. Click on it for a bigger image!
And here you got the bootloader. I set it to 410MHz, which I think is a safe value.
Still a big performance improvement from the stock 350MHz!
Remember that I'm sharing it because it worked like a charm for me. But no warranties of any kind, try at your own risk!
Good luck! .
(Last edited by dabyd64 on 26 Feb 2013, 17:07)