Recently, Intel does not offer the PCH driver running in CentOS 5.5 x86_64. Only RHEL 6/6.1 does not the driver for installation. You can switch Intel HostRAID to LSI instead. For LSI PCH driver, please download from here: https://www.supermicro.com/wdl/driver/SATA/LSI_PCH_RAID/Driver/Linux/