Magnetic disc unit system

摘要

A magnetic disc unit capable of improving the throughput by minimizing the seek time for the magnetic head. The magnetic disc unit is operative to respond to a cylinder address instructed by the host unit to move the magnetic head to the corresponding cylinder position on the magnetic disc comprises a cylinder address/position assignment selecting circuit for changing the address instructed by the host unit into a new address so as to desirably change cylinder address/position assignments. A head location controlling circuit is responsive to the new address to move the magnetic head to a cylinder position corresponding to the new address. In one mode, the cylinder address/position assignment selecting circuit performs renewal of cylinder addresses such that the magnetic head passes along the magnetic disc through all of the cylinder positions designated by cylinder addresses by making a return trip between inner and outer circumferences of the magnetic disc. In another mode, the cylinder address/position assignment selecting circuit performs renewal of cylinder addresses that when the innermost cylinder address is substituted for a cylinder address instructed by the host unit, the access time for the substitutive cylinder address is minimized.