Miniserver VM minimum CPU allocations are directly proportional to their RAM allocation, with 512MB coming with roughly the same compute resource as a 2002 1.4GHz Pentium 4 processor, and 4GB being about the same as a single core of a modern 2.8GHz Xeon processor.
We also give higher-end Miniserver VMs multiple virtual cores so that they can run multi-threaded applications more effectively. All individual virtual cores can also burst to a maximum of a whole single 2.8GHz Xeon core.
By way of comparison with another unit of compute resource, one Amazon 'ECU' is roughly equivalent to a Miniserver VM with 2GB of RAM (VM4000).