1. An I/O control system for controlling I/O devices in a multi-partition computer system comprising: an IOP partition comprising an IOP cell containing at least one CPU executing a control program; and a plurality of standard partitions, each including a cell comprising at least one CPU executing a control program, coupled, via shared memory, to the IOP cell; wherein at least one of the standard partitions becomes an enrolled partition, communicatively coupled to the IOP cell, in response to requesting a connection to the IOP cell; and wherein I/O requests directed to the I/O devices from the enrolled partition are distributed over shared I/O resources controlled by the IOP cell.