Originally (until 1990/91) there was what is now understood as an interface to the disk drives in consumer-not on the hard disk. For this, a controller was needed in the form of an ISA card. This said, the disk controller, inter alia through a ST506 interface level (with the modulation standard MFM, RLL and ARLL). The capacity of the disk was dependent on the controller, and the same was true for the data reliability. A 20mb MFM drive could store on an RLL controller 30 MB, but possibly with a higher error rate.
Due to the separation of controller and the latter medium for PCB Assembly had to be low-level formatted before use (soft sectoring). In contrast to these earlier hard drives with stepper motors modern hard drives are equipped with linear motors that make a (magnetic) hard sectoring during the PCB Assembly and preparation required and can not be low-level formatted.
The ESDI controller fr PCB Assembly was relocated to the drive to increase speed and reliability. Only SCSI and IDE disks broke up with this tradition from the early days of magnetic disk-based storage technology. Set instead of the previous one controller host bus adapters that provide a much more universal interface. HBAs exist as plug-in cards or integrated on motherboards or chipsets and are often still referred to as a “controller”.
Serial ATA interfaces are used almost exclusively for internal hard drives and PCB Assembly in the desktop area today. However, the IDE interface is still widely used in game consoles and hard disk recorders.
For servers and workstations, SAS and Fibre Channel are next to SATA. The Boards were provided for a long time with ATA interfaces, they are now almost completely replaced by (up to 10) SATA interfaces.
A fundamental problem in parallel transmissions is that it is becoming increasingly difficult with increasing speed to dominate different times of individual bits through the cable, and crosstalk. Therefore, the parallel ports came more and more to their limits. Serial lines, in particular in connection with the differential line pairs, now allow much higher data rates.
Machine instructions refer to a specified source or target objects, they either use and/or act on. These objects are shown in coded form as a part of the machine instruction, and therefore its effective (logical) memory address has to be determined on or before the actual execution of the command.
The result of the calculation is provided in special elements addressing the hardware (registers) and used in the command execution. To calculate, various addressing modes (variants) are used, depending on the structure of the command that is defined in a instruction code.
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