Applications performance under OSF/1 AD and SUNMOS on Intel Paragon XP/S-15

On Paragon, two operating systems are available: OSF/1 AD and SUNMOS. The chief drawbacks of OSF/1 AD are: OSF/1 AD takes about 8 MB of memory on each node of the Paragon; messages can be sent only at a bandwidth of 30-35 MB per second compared to 200 MB per second peak advertised rate; latencies are on the order of 100 microseconds using Intel NX calls under OSF/1 AD. All these drawbacks can be minimized by using SUNMOS. SUNMOS takes only 250 KB of memory on each node and can send messages at bandwidth of 170 MB per second with latencies of 70 microseconds. We have measured the performance of applications under OSF/1 AD and SUNMOS and found that under OSF/1 AD, performance does not scale as the number of nodes increases, whereas under SUNMOS it seems to scale because of higher communication bandwidth