Apparatus having a circular buffer that maintains a one entry gap between elements written to the microprocessor and elements operated on by the clock

Claim 1

Apparatus comprising: a hard disc drive including disc media for storing data; a disc controller connected for controlling said hard disc drive; a clock connected for running said disc controller, said clock running at a relatively slow variable rate; a microprocessor connected for providing writes into said disc controller, said microprocessor having a maximum operating rate higher than the rate of said clock; and an interface circuit for interfacing said microprocessor to said disc controller, said interface circuit employing a circular buffer having a plurality of elements to be written to, said circular buffer maintaining a one entry gap between ones of said elements which are being written to by said microprocessor and those of said elements which are being operated on by said clock; whereby said interface circuit allows a limited number of back-to-back writes of said microprocessor with zero wait states of said microprocessor at the maximum rate of said microprocessor; whereby said interface circuit allows an unlimited number of writes of said microprocessor with zero wait states of said microprocessor at a rate equal to or less than the rate of said clock; whereby said interface circuit provides a ready line to throttle back the writes of said microprocessor to a rate equal to the current rate, if the writes of said microprocessor occur at a rate faster than said clock.