This implementation uses used software SPI (bit banging).
It uses hardware SPI (C̅S̅ → pin 52) through the ICSP header since commit 2f98c47.
I needed to flash my laptop's BIOS and the Arduino Due was the only one I had running at 3.3V.
Yet I lacked any female jumper cables, since it has the SPI pins on the ICSP header.
The full v1 protocol specification is detailed in serprog-protocol.txt.
Use this with flashrom, following these instructions.
Pictures
