st506

The ST-506 was the first 5.25 inch hard disk drive, introduced in 1980 by Seagate Technology (then Shugart Technology). It stored up to 5 megabytes after formatting and cost US $1,500 ($ in today's dollars). The similar, 10-megabyte ST-412 was introduced in late 1981. The ST-225 was introduced shortly thereafter with 20 megabytes and half the height. All three used MFM encoding, a widely used coding scheme. A subsequent extension of the ST-412 interface used RLL encoding for a 50% increase in capacity and bit rate.