I have an Intel Q9650 core 3ghz overclocked to 4.5ghz quad processor. I have been running windows 8 64 bit since it was available as an upgrade from windows 7 64 bit. I am unable to download and upgrade to windows 8.1 as I get a message saying that my processor does not support cmpxchG16b. I have run Coreinfo and that confirms this. However, someone who has the exact same processor as me has run Coreinfo and his reports that his processor does support cmpxchG16b. So, could it be a motherboard issue? Do I have to alter something in the bios to enable support for this? My mobo is an Abit IP35 Pro XE. I would be grateful for any advice.