I have a dell dimm 8400 desktop. over time I have added memory to it. Last time was a couple of years ago . the machine came with One 512 stick and somewhere along this time line I must a added a 1gb stick. I just added 2 more 512 sticks. I am now curious being that I have three 512 sticks and One 1gb stick is this messing up my capabilities. After adding the two 512 sticks I do not believe I'm getting that much better performance. Look forward to your comments. Gary