I managed to run Rockbox on iRiver iFP790. Currently it is possible to
browse the menu. More information at:

http://www.rockbox.org/twiki/bin/view/Main/IriverIfpPort

Things that work:
- interrupts (at least the timer interrupt)
- LCD screen with backlight
- keys

Things that are not supported yet:
- flash memory
- audio input/output
- FM tuner
- RTC

Supporting flash memory requires dealing with bad blocks. Big flash
chips may contain bad blocks and the firmware is expected to remap the
blocks so that the bad ones are skipped. The remapping has to be done
in the same way as in the original firmware in order to preserve
compatibility. This will probably be the biggest difficulty.

I do not know much about audio output yet, but I have found some parts
of the firmware responsible for this.

Key definitions for plugins are not done and because of that plugins
do not compile.

I will release the next version of the iFP emulator, capable of
running Rockbox soon.

Have fun.

-- 
Tomek Malesinski