Windows Server 2012 and Windows 8 came with a lot of changes to the task manager and I find it a great improvement. In some cases the default views have been simplified further than power users and administrators would prefer. One example is by default you only see the total processor utilization and don't see the individual cores.
To see all of the CPU cores right click on the CPU graph and click "Change graph to > Logical processors".
You will now see the graph of all of your CPU cores.