select queries are slow

[mysql support]

Hello Everyone,

RAM 32 Gb
No of Processors(CPUs) 24
OS RHEL 5.xx
Mysql database 5.0
Current my.cnf file


mysqld]

{items removed}

log-warnings
skip-name-resolve
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Default to using old password format for compatibility with mysql 3.x
# clients (those using the mysqlclient10 compatibility package).

key_buffer = 256M
table_cache = 256
#table_cache = 2048
max_allowed_packet = 10M
sort_buffer_size = 256M
read_buffer_size = 32M
read_rnd_buffer_size = 16M
myisam_sort_buffer_size = 256M
thread_cache = 96
query_cache_size= 48M
max_heap_table_size=20M
tmp_table_size=48M
# My settings
#thread_stack=128K
max_connections=16192
wait_timeout=40
back_log=600
connect_timeout=8
#delayed_insert_limit=200
#delayed_queue_size=2000
#flush_time=0

skip-bbd
# Try number of CPU's*2 for thread_concurrency
thread_concurrency = 24
innodb_buffer_pool_size = 1536M
innodb_log_file_size = 100M
innodb_flush_method = O_DIRECT
innodb_file_per_table = 1
innodb_flush_log_at_trx_commit = 2
innodb_log_buffer_size = 32M
innodb_additional_mem_pool_size = 20M

# num cpu's/cores *2 is a good base line for innodb_thread_concurrency
innodb_thread_concurrency = 16


[mysql.server]
user=mysql
basedir=/var/lib

[mysqld_safe]
err-log=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid


Why select queries are slow with MyISAM storage? Is need to change some parameters ? Kindly review and send me with recommenmdation which is suiable