More properly known as ST506/412, this was the first hard disk interface standard
to be used in microcomputers
. It was created by Seagate Technologies
. At that time, the cost for a five megabyte
drive was over one thousand dollars.
The hard drive itself was a full height 5 1/4 inch drive, powered by a stepper motor
. It connected to the drive controller
, a separate plug-in card, through two ribbon cables
, a 34-pin control
cable and a 20-pin data cable. Although the control cable could be shared between two drives, each drive required its own data cable. Data transmission was serial
, at up to 7.5 Mbps(megabits per second). Compared to the up to 100 MBps(megabytes per second) transfer rate of UDMA5
and the up to 320 MBps transfer rate of SCSI-3
, this seems insignificant, but considering the initial drive capacity, the entire contents of the drive could be transfered in less than six seconds.
Two recording methods were used, MFM
. By using RLL, you could get a 50% increase in storage capacity
at the cost of some error checking
, but use of RLL on non-RLL compatible drives resulted in bad publicity for the standard.
By the late eighties, ST506 had started to be crowded out by ESDI
, and by the early nineties, both were made obsolete