I am using the latest Parallels 10.2.0 build on the latest MacBook Pro quad core 16GB RAM, so I do have plenty of resources. My virtual machine is Windows Server 2008 R2 shows 99% of CPU idle, but my Parallels run at 400% CPU and kicking off the fan all the time. The MacBook Pro casing heats up pretty bad too. I've tried various KB articles suggested in other posts (e.g. reducing to 2 CPUs, disabling real-time free space optimization etc.), but still Parallels are overloading my CPUs. I love Parallels and the Coherence mode, but the performance needs to be improved ASAP. This makes Parallels almost unusable for me and others, according to the posts I've read so far.