the ST506-Schnittstelle was sketched 1982 by the company Seagate for their 5 ¼ to tariff non removable disks ST506 (5 MT) and ST412 (10 MT) and applied long time as in fact standard.

It is an advancement of the diskette interface and sets very deeply in the hardware. Thus the heads are steered via clocks in the cable and the recording method (MFM or RLL) is determined by the CONTROLLER in the computer.

With the ST506 can up to four drive assemblies be addressed and them uses two different cables. The A-cable (34 polig) is ground through from drive assembly to drive assembly (daisy chain) and must at the end (on the last non removable disk) be scheduled. It serves for to the addressing and controlling of the drive assembly and/or. Head. In order to be able, become to differentiate the two drive assemblies between the two non removable disk connections some veins of the flat cable rotates.

The B-cable (20 polig) is point of point a connection between CONTROLLERs and non removable disk and transfers the writing and read data (bit by bit). For the enterprise of 4 non removable disks 5 connections at the CONTROLLER are thus needed (once A and four times B). Because of BIOS - and operating system - restrictions were however in the PC no more than two non removable disks usually.

The addressing of the data on the non removable disk was made by head, trace and sector. As coding MFM with 17 sectors per trace or RLL with usually 26 sectors per trace was used. CONTROLLERs and non removable disk had to be appropriate for coding in each case. From the fixed rate of mostly 3600 rpm a data rate of approximately 500 resulted and/or. 750 kByte/s.

IBM derived its own interface named ESDI , which was only mechanically compatible. With 34 sectors per trace the capacity and data rate could be increased.

Successor of this interface is Integrated drive Electronics (IDE).


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