Serial ATA
 
  ATA-IDE uses a 16 bit parallel data bus.  The bus cable is a flat ribbon
    of parallel wires.

  As transfer speeds increase, inductance between wires causes noise and 
    data loss.

  UltraDMA 66 and up uses an 80 cable and CRC to guard against data loss.
    The 40 additional ground lines help to isolate each data line.

  Serial ATA discards the parallel lines for a single data line with 
    transfers at much higher speed.  Because there is only one data line,
    it is much easier to shield the line against noise.

  Note, ethernet, firewire, and USB are all serial and various techniques
    have made them very efficient. 

  Specs: (tom's hardare)
    150MB/s achievable with a goal of 300/600 MB/s future.
      Still slower than UltraDMA/100 
    Hot plugable.
    7 wire connector.
    Cable up to 1 meter long (3 foot).