I've had this problem for a long time, but I don't feel like to ask it
until some one ask me about this problem.
Lenovo T520 has a BIOS chip under the magnesium structure frame, and
it may have a WSON package, so I solder a pin connector at the `J100'
solder place. (https://www.coreboot.org/Board:lenovo/t520#Flashing
However, I don't know whether it can cause problems. I flashed two
pieces of T520 mainboard (without nVIDIA GPU) before, and after it had
coreboot installed, the system could hang randomly, I don't know what
had happened. I hadn't tested it with the pin connector soldered and
So I hope some one with this laptop can report some status in using.