A Mark 1 System X unit is a vast construct with suites of 8 racks in length, and it can be over 15 suites from end to end. This is far from ideal, as each of those suites needs to be powered and costs quickly add up. Further to that is the consideration that all the powered equipment generates heat, which will require more power costs to remove from a room – these are the two main reasons that Mark 1 exchanges are being closed down in favour of Mark 2.