32MB ROM dump, start address 0xfc000000 (bootloader). Firmware starts at 0xfc020000. Created after upgrading to the latest publicly available firmware.
http://www.sendspace.com/file/f9mx90A note: the sx270 and sx280 may share the same firmware, the first 16MB of the 100c sx280 ROM is identical to the first 16MB of the 100c sx270 ROM...
Another note: this doesn't mean any CHDK development for this camera yet.