By David Russell, reporter at OptionMonsterNEW YORK -- Nvidia ( NVDA) has been holding support around $12, and now the bulls are looking for the graphics chipmaker to rally. OptionMonster's tracking systems detected unusual activity in the semiconductor stock on Thursday and Friday. First they bought the June 12 calls for $1.11, then they came back the next day to snap up the September 13 calls for $1.05 and $1.06. Volume exceeded open interest both sessions, indicating that new money was put to work. The calls, which lock in the price where the stock can be purchased, can generate major leverage in the event of a rally. But they also have the potential to become worthless if the stock doesn't move. Shares of Nvidia rose 1.8% to $12.41 on Friday. The stock has bounced near the $12 area several times in the last 18 months, which could be leading some traders to think that it's due for another rebound. The last earnings report in November was mixed, with earnings and revenue better than expected but guidance below consensus estimates. Total option volume was more than quadruple average amounts on Thursday and Friday. Calls accounted for more than 80 of the activity in both sessions. Russell has no positions in NVDA.