HP 7957A - Introduction The HP-7957A was introduced in 1987 as a modular 81 MB hard disc drive connected primarily to HP 300 Series machines. It had an HP-IB interface with an average seek time of 29ms and a data transfer rate of 1.25 Mb per second. Inside the HP-7957A is a Micropolis 1353A, an ESDI 5¼" hard disc with capacity of 106 MBytes. An introductory price is unknown.