For the transfer of data to and fro from the devices controllers are required to control the ports for connecting the devices. For the ports already present in the motherboard, usually the controller is on-board the motherboard too. The ports for hard-disk drives and optical drives include:
Parallel ATA (PATA/IDE):
- 40 pin cable and port
- max cable length: 45cm
- max number of hard drives: 4 (only in some motherboards, 2 per cable)
- max transfer speed: 133 MB/s
Serial ATA (SATA):
- 7 pin cable and port
- max cable length: 1m
- max number of hard drives: 8 (till now, one per cable)
- max transfer speed: 150-600 MB/s
SATA ports are fast replacing PATA ports. Controllers for extra ports like additional SATA or PATA ports, SCSI, USB, etc. that have been added via PCI card or similar are built on the PCI card itself.
There are ports for additional storage expansion as well like USB and SCSI. SCSI is mainly used with servers that have large arrays of hard-disk drives whereas USB controller is already present on the motherboard. The latest USB 3.0 specification is supposed to achieve 600 MB/s.