Figure 8: Latency versus message length for Comms1 for various maximum size packets.
Figure 8 shows the
Comms1 latency versus message length. For message length 1, the
graph shows the minimal latency. The minimal latency for all packet
sizes up to 512 bytes is 67 
s. The minimal latency for
1024, 2048 and 4096 sized packets is higher. Similar results have
been obtained for Comms2.
The higher latency for large packets, see
Figure 5, is caused by the padding of
flush. This overhead can be removed by modifying the
protocol, so that the packet's header contains the packet's
length. This change will make the minimal latency 67 s,
independent of the packet size.
The T9000 transputer has a minimal Comms1 latency of
7.4 s; two directly connected T9000 transputers will even
improve on this. The factor of 10 difference shows the performance
lost due to the use of standard OS facilities, implemented in
software, instead of dedicated hardware, i.e., the hardware
communication system and the hardware scheduler.