multicore virtual CPUs, vSphere 4.1
vSphere 4.1 now allows you to configure the Number of Virtual CPUs per Virtual Socket. You can configure virtual machines to have multiple virtual CPUs reside in a single virtual socket, with each virtual CPU appearing to the guest operating system as a single core.
Using multicore virtual CPUs can be useful when you run operating systems or applications that can take advantage of only a limited number of CPU sockets. Previously, each virtual CPU was, by default, assigned to a single-core socket, so that the virtual machine would have as many sockets as virtual CPUs.