I have recently upgraded from two 4 GIG sticks to three different 4 GIG sticks. The computer seems slower than it did before. he is the type of RAM i bought G.SKILL Ripjaws Series 12GB (3 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9T-12GBRL.