Is this Mysql database server load too high?

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http://serverfault.com – I'm running a php website. I have two servers. Please help me to check is this Mysql Database Server load too high? I found the mysql CPU usage is always higher than 100%. Any suggestions to optimize? I'm using CentOS release 5.8 Mysql 5.1.63-cll MySQL Community Server 4 Processors Intel Xeon 2.13G Total Memory: 4 G my.cnf myisam_sort_buffer_size = 64M thread_cache_size = 8 query_cache_size= 100M thread_concurrency = 4 max_connections = 600 max_user_connections=600 (HowTos)