So you have already tried using for example the my-huge.cnf instead? If that didnĀ“t utilize more memory, then the problem may lie somewhere else or there is actually not a problem at all.
At least, the variables are explained in detail here:
http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html Most important are those variables with "buffer" in it. For example
key_buffer_size and
read_buffer_size.