# apache 1.3.x
apache_1.3.x/src/include/httpd.h
HARD_SERVER_LIMIT 256

# apache 2.0.x
- prefork
httpd-2.0.63/server/mpm/prefork/prefork.c
DEFAULT_SERVER_LIMIT 256

- worker
httpd-2.0.63/server/mpm/worker/worker.c
DEFAULT_SERVER_LIMIT 16
DEFAULT_THREAD_LIMIT 64