well, i had kind of cleaned up the rtc extension for the 3p4w clock, now it's 8p9w.
had stayed on my bedside for a week, using the alarm everyday, had not really measure the accuracy but does not need to adjust it for the week.
there's also software i2c code (quite cleanly isolated) if anyone need to salvage a software i2c master.
project here
http://www.simpleavr.com/msp430-projects/rtc-clock