in general , the present invention provides an efficient usage of far end crosstalk coefficient memory in a g . fast vectoring system . according to certain aspects , embodiments of the invention provide a simple scheme for efficient management of the discontinuous and regular operation fext coefficient memories to handle the complexity of lines joining / leaving the system in both regular and do groups . in embodiments , by disabling the power - efficient , discontinuous operation , a g . fast system according to the invention first frees up the do coefficient memory . next , the system uses this memory as the staging area to manage joining / leaving events . finally the system re - enables to the power - efficient discontinuous operation and re - populates the do coefficient memory .