I was told that when rolling dice [for a game, such as backgammon] on shabbos one should roll one di, move the pieces, and then roll the other di [and move the pieces]. The reason for this, I was told, is in order to remind you not to write down the numbers on the dice, to add them.
This doesn't make a whole lot of sense to me, since the numbers are already on the dice, so writing them down to add them would accomplish nothing! Furthermore, adding one digit numbers by writing them down doesn't help one to add them any more than simply doing mental math! So why is this a concern, and what are the sources for such a practice?