Mid-late 2011 27" iMac with Core i7 processor. Has four banks, but only two are occupied (2x2GB). Maximum memory allowed is 16GB. Can I use 2x8GB modules (using only two banks), or must I 4x4GB (using four banks)? I am not planning on re-using the factory installed memory. ---------- Never mind. This Apple link suggests all four banks need to be occupied as it does not allow for 8GB modules.