This is a quick status update on my attempts to run the latest SeaBIOS on the Acer c720 chromebook (aka Google peppy). In brief, the latest SeaBIOS runs well on the c720, and it also enables booting from SD cards (which oddly doesn't seem to work in the version of seabios shipped with the c720).
At this point, I've only upgrading SeaBIOS. I haven't updated the version of coreboot in the c720.
For those interested in reproducing, it will require the very latest seabios from the git repo. Because only a small portion of the flash is used for seabios and that portion is in a non-standard location, the new seabios CONFIG_CBFS_LOCATION config option needs to be set to 0xffe00000 and some additional steps are needed to build the final rom. I've attached a script with the steps I run to build and install seabios for the c720 (based on instructions from Stefan Reinauer).
In some initial tests, I can install and run Fedora on the c720, but there are some quirks. Suspend/resume is quirky (very slow to resume), the touchpad isn't working (needs a driver), and the keyboard mappings seem to be a little quirky. I don't think this is seabios related though. Also, systems using syslinux for a boot loader don't like the fact that the c720 reserves chunks of memory under 16Meg (which requires setting an explicit "mem=1600m" in the kernel boot parameters), however that doesn't seem to be a problem once the OS in installed (and no longer uses syslinux).
The seabios xhci testing branch does detect the xhci controller. However, the current c720 boot code maps all the xhci devices to an ehci controller. I'm going to see if I can convince the boot code to map the devices back to the xhci controller so that I can test the seabios code on the Haswell xhci controller.
-Kevin