Apache 2.0.59 (SLES 9)
MaxClients = ThreadsPerChild*StartServers
ThreadsPerChild threads in each process, so MaxClients / ThreadsPerChild = the number of processes you will top out at
min/max need to be multiples of threadperchild. maxsparethreads < maxClients means you see child processes being reaped when there's a momentary lull, which will sever your keepalive connections.
1600 concurrent connection setup: