I bought 2x4GB DIMMs for my workplace 2009 MP 4 core (4,1) and I discovered later that 4 core 2009 Mac Pros only support 2GB sticks and a total of 8GB. macsale's RAM chart is misleading -- it says "8-core only" under certain upgrades, implying the other upgrades are fine for either 4 or 8 core. I should have checked Apple's website first. Arg. Long story short is that the box is acting odd. I have 4GB sticks in slots 1 & 3 and it registers 8GB. All is fine for a few hours but then a sudden, massive latency kicks in crippling the OS and forcing me to hard power off. 1. Is this because I'm using 4GB sticks when it wants 2GB sticks? 2. How in the world can a 2009 Mac support only 8GB of RAM?? Seems so... 32 bit... (this is my web development workplace comp and I'm reluctant to have my boss RMA the sticks for a 4x2GB upgrade).