to create a new i586-generic board:
$ cd chromiumos/src/overlays
$ cp -a overlay-x86-generic overlay-i586-generic
$ cd overlay-i586-generic
$ echo i586-pc-linux-gnu > toolchain.conf
$ echo FULL_BINHOST= > prebuilt.conf
$ vim make.conf
- edit MARCH_TUNE to match your cpu
- update VIDEO_CARDS to include the drivers you care about
then run ./setup_board --board=i586-generic && ./build_packages
--board=i586-generic
g'luck
-mike