Apparatus for creating subatmospheric high plasma densities in the vicinity of a substrate in a work space for use in magnetron sputter deposition aided by ion bombardment of the substrate. According to the method of the present invention, data can be read in the middle of a plurality of write commands provided that the addresses of the readwrite data locations do not overlap. In each case the linear equations do not to be used with reference to look up data tables thereby reducing the memory space required and also reducing the computational power required in processing systems.