So, I have a 2009 macPro and it is getting really slugish and hoging my hard drives, as I have 6gb of RAM, but that is obviously not enough for my 16bit 20-80mpix Photoshop PSD files. I know it's a lack of ram, as it works perfectly when I edit at 8bit, or smaller resolution files(I checked the Appication monitor). HOW DO I EXPAND THIS RAM??? I have no idea what modules work for my Mac? And all the info around the forums I've found links to manufacturers I don't have at my disposal. Is it any DDR3? But what if it's a t 2000+mhz? Will it still work at lower speeds that my computer supports? Could I just add a 16gb into an empty slot? Or, do I need to sell of my existing ram? (I only have the budget for 16gb, be it in a single module or 2x8gb)? Also, I live in an isolated country, so I can't order anything online(shipping and customs would add 100% to the price). Could these work? KINGSTON 16GB (2x8GB) 2400MHz DDR3 HyperX Beast KHX24C11T3K2/16X KINGSTON 16GB (2x8GB) 1866MHz DDR3 HyperX Predator KHX18C9T2K2/16X KINGSTON 16GB (2x8GB) 1600MHz DDR3 KHX16C9T3K2/16X I also have an option for IBM and HP, but I'd rather avoid them if possible, especially HP.