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As a result, early floppy drives required jumpers to be set on the drive to tell it which controller commands it should receive. When introducing the PC, IBM sliced the cable between the first and second drive, and twisted seven of the conductors, effectively flipping the four conductors which specifically addressed the first or second drive.
English: Diagram illustrating the basic internal parts of a 3.5" floppy disk. Document labels rendered as numbers to aid in internationalization. Note: The unlabeled square in the upper left is the approximate location of the write protection tab.
When the controller and disk drive are assembled as one device, as it is the case with some external floppy disk drives, e.g., Commodore 1540 and USB floppy disk drives, [27] the internal floppy disk drive and its interface are unchanged, while the assembled device presents a different interface such as IEEE-488, parallel port or USB.
A disk controller is a controller circuit that enables a CPU to communicate with a hard disk, floppy disk or other kind of disk drive. It also provides an interface between the disk drive and the bus connecting it to the rest of the system. [1] [2] Early disk controllers were identified by their storage methods and data encoding.
A floppy-disk controller [2] An IEEE 1284-compatible parallel port [2] (commonly used for printers) One or more 16C550-compatible serial port UARTs [2] Keyboard controller for PS/2 keyboard and/or mouse; Most Super I/O chips include some additional low-speed devices, such as: Temperature, voltage, and fan speed interface [3] [4]
In DOS, it serves as the low-level interface for the built-in block device drivers for hard disks and floppy disks. This allows INT 25h and INT 26h to provide absolute disk read/write functions for logical sectors to the FAT file system driver in the DOS kernel, which handles file-related requests through DOS API functions.
The WD1761-WD1767 series were versions of the FD179x series rated for a maximum clock frequency of 1 MHz, resulting in a data rate limit of 125 kbit/s for single density and 250 kbit/s for double density, thus preventing them from being used for 8-in (200 mm) floppy drives or the later "high-density" 5.25-inch (133 mm) or 90 mm floppy drives.
Single head drive, but double-sided floppy discs (total of 360 kB per floppy) Amstrad PCW8512/9512: 3 inch Double 2 80 9 512 720 kB 300 MFM 720 kB mode uses both sides - ensure disc inserted correct way up. Apple II: 5 1 ⁄ 4 inch Double 1 35 13 256 soft 113.75 kB 300 GCR [NB 2] 1 16 140 kB 3 1 ⁄ 2 inch Double 1 80 Variable (8-12) 512 400 kB