ich würds mal mit folgenden Einstellungen probieren:
key_buffer = 16M
max_allowed_packet = 1M
table_cache = 64
sort_buffer_size = 512K
net_buffer_length = 8K
read_buffer_size = 256K
read_rnd_buffer_size = 512K
myisam_sort_buffer_size = 8M
ansonsten gibt es auch ne Faustformel für die Parameter:
key_buffer - 64M for 1GB, 128M for 2GB, 256 for 4GB
join_buffer_size - 1M for 1GB, 2M for 2GB, 4M for 4GB
sort_buffer_size - 1M for 1GB, 2M for 2GB, 4M for 4GB
read_buffer_size - 1M for 1GB, 2M for 2GB, 4M for 4GB
read_rnd_buffer_size - 768K for 1GB, 1536K for 2GB, 3072K for 4GB
myisam_sort_buffer_size - 32M for 1GB, 64M for 2GB, 128 for 4GB