A dedicated processor might be an interesting solution for off-loading more DSNIC functionality to the board. The CPU time for handling a packet allows us to relate the CPU power of such a dedicated processor to the packet size that can be handled by this processor, assuming the same communication protocol is used. This would result in a system in which the board takes care of all the packet handling, and the interface between the CPU and the board allows message communication.
Suppose the dedicated on-board processor is n times slower than
the 200 MHz Pentium Pro. This means that it requires 
to handle a packet. To be able to keep up with
the full bidirectional DS link bandwidth, 16.6 Mb/s in our
case, we can calculate the required minimal packet size:
.
The typical message length used for real-time analysis in ATLAS is 1 kbyte. For ATLAS, the dedicated processor is therefore required to be capable of handling packets of this size adequately. A communication processor that is 5.4 times slower than the Pentium should just be capable of link saturation. It is expensive to use a dedicated processor to achieve the optimal packet size of 28 bytes, since it requires a processor with about 7 times the power of the Pentium. If such a small packet size is required, one has to use dedicated hardware.