To get rid of some of the complications of this last method, PVM was created. PVM (and the Beowulf clusters that run it) are based on an uniform API that allows multiple process to communicate with each other in a more transparent way. However, there is no mechanism for communicating between machines of varying architectures, especially when these machines differ in the way they order the bytes in a word or double word, known as little endian and big endian machines. There needs to be one uniform API for multiple processes on multiple architectures to communicate with each other in a transparent way.
Granted it is probably possible to modify and port the Linux PVM libraries to other architectures such as PPC, SPARC, MIPS, XScale, and Ia64. However these systems will still need to be running Linux for the API to communicate properly with the OS. Some companies and organizations would love to be able to get the benefit of PVM but are unwilling to switch to Linux and are happy with their current OS. Because of this, we must look in to a new method of PVM for a heterogeneous network.
HPVM will try to solve these problems by designing a Heterogeneous Parallel Virtual Machine (hereafter known as HPVM). The main goal is for a user to be able to create a single super machine from a collection of smaller machines."