Ok. I did it and I got the serialICE prompt (@38400). In fact it appears again and again every second or so. That suggests some watchdog might be rebooting the board. I already set the it8712f kill watchdog call in coreboot, not sure if it was needed, but it seems it is. I could put it in serialICE but unless I need to use SerialICE for something else I think I won't.
Well please investigate because I put there already - it is the write to reg 0x72. There might be watchdog in SB700 datasheet says disabled by default but dunno if there is some possibility that it is enabled by default by some strap resistor.
Make sure you call sb700_lpc_init _before_ any access to superIO. Also I would suggest to use the tilapia_fam10 instead of a copy - you might forgotten to do something. Simply do changes to the tilapia_fam10 and rename/move to another dir late
The code in the SerialICE does same thing as sb700_lpc_init and it8712f_enable_serial.
Thanks Rudolf