This paper presents the communication architecture of the
StarT-Voyager system, a parallel machine composed of a cluster of
unmodified IBM 604e-based SMP's connected via a high speed
interconnection network.  A custom network interface unit (NIU) plugs
into a processor card slot of each SMP, providing a high-performance
message passing substrate that supports both fast user-level message
passing and cache-line coherent shared memory.  The substrate consists
of four hardware implemented message passing mechanisms to achieve
high performance over a wide spectrum of communication patterns.
StarT-Voyager also introduces a novel protection scheme which improves
upon past designs by not requiring strictly synchronized
gang-scheduling, and by allowing system code and multiple user
applications to share the network simultaneously without compromising
protection nor performance.  Performance predictions based on
synthesized Verilog code show StarT-Voyager's novel message passing
mechanisms offer a definitive advantage in a multi-threaded
environment without compromising the performance in a single-threaded
environment.  Preliminary shared memory simulations are also
promising.  StarT-Voyager hardware will be available in September,
1998.

<p><hr>

The author's web site:

<a href="http://www.csg.lcs.mit.edu/StarT-Voyager/1996/startvoyager.html">www.csg.lcs.mit.edu/StarT-Voyager/1996/startvoyager.html</a>