Beowulf had no shared memory abstraction, programs had to be written using message passing, e.g. MPI.

I'm not convinced a shared memory abstraction is a good thing for distribution across machines. Some Beowulf clusters actually had much lower latency interconnects than ethernet, e.g. Quadrics, but we still needed to carefully optimise the traffic. With a shared memory abstraction, such optimisation is out of our hands.

Beowulf was just the idea of making a cluster of cheap commodity hardware using open software, typically not Single System Image.

Yeah I was thinking this sounds more like MOSIX, but with the added abstraction to handle executing the same code accross different architectures.

http://www.mosix.cs.huji.ac.il/txt_about.html

Indeed, MOSIX or Kerrighed http://www.kerrighed.org/wiki/index.php/Main_Page