Floppy disk hardware emulator
Encyclopedia
A floppy disk hardware emulator is a device that emulates a mechanical floppy disk
drive with a solid state
or network storage device
plug compatible with the drive it replaces, similar to how solid-state drive
s replace mechanical hard disk drives.
s, electronic keyboards and industrial automation often used floppy disk drives for data transfer. Older equipment may be difficult to replace or upgrade because of cost, requirement for continuous availability or unavailable upgrades. Proper operation may require operating system
, software and data to be read and written from and to floppies, forcing users maintain floppy drives on supporting systems.
Floppy disks and floppy drives are gradually going out of production and replacement of malfunctioning drives, and the systems hosting them, is becoming increasingly difficult. Floppy disks themselves are fragile, of may need to be replaced often. An alternative is to use a floppy disk hardware emulator, a device which appears to be a standard floppy drive to the old equipment by interfacing directly to the floppy disk controller
, while storing data in another medium such as a USB thumb drive, Secure Digital card
, or a shared drive on a computer network. Emulators can also be used as a higher-performance replacement for mechanical floppy disk drives.
/ FM
/ GCR
encoded signal to the drive to write data, and expects a similar signal returned when reading the drive. On a write, a hardware PLL or a software-based filter component undoes the encoding, and stores the sector data as logically written by the host. An inverse mechanism translates the stored data back into an encoded signal when the data is read. Noisy raw data signals are filtered and cleaned up before conversion.
Most FDC interfaces do not directly address tracks, rather provide "step-in" and "step-out" pulses. Those, and the current sector number virtually rotating under the emulated read/write head, are tracked by the emulator in order to determine which sector is to be accessed.
Because the interface to the floppy drive is very low-level, emulators must maintain the approximate timing of floppy disk operations. This may require the emulator to provide buffering, with some delay in updating the permanent storage.
The emulator saves the data written to the floppy in either local storage (stand-alone emulators), or in a remote storage device or data exchange module (stateless emulators).
Direct access and ISO image implementations can also emulate system / non-standard floppies, whose file system can't be simply translated.
ISO image implementation can also be coupled with a virtual drive
to seamlessly emulate floppy drives on a computer.
Some devices can store multiple floppy images, and provide a mechanism to select which emulated floppy is mounted on the emulated drive.
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
drive with a solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
or network storage device
Disk storage
Disk storage or disc storage is a general category of storage mechanisms, in which data are digitally recorded by various electronic, magnetic, optical, or mechanical methods on a surface layer deposited of one or more planar, round and rotating disks...
plug compatible with the drive it replaces, similar to how solid-state drive
Solid-state drive
A solid-state drive , sometimes called a solid-state disk or electronic disk, is a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the same manner of a traditional block i/o hard disk drive...
s replace mechanical hard disk drives.
History
Older models of computerComputer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s, electronic keyboards and industrial automation often used floppy disk drives for data transfer. Older equipment may be difficult to replace or upgrade because of cost, requirement for continuous availability or unavailable upgrades. Proper operation may require operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, software and data to be read and written from and to floppies, forcing users maintain floppy drives on supporting systems.
Floppy disks and floppy drives are gradually going out of production and replacement of malfunctioning drives, and the systems hosting them, is becoming increasingly difficult. Floppy disks themselves are fragile, of may need to be replaced often. An alternative is to use a floppy disk hardware emulator, a device which appears to be a standard floppy drive to the old equipment by interfacing directly to the floppy disk controller
Floppy disk controller
A floppy disk controller is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive . This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8072A or 82072A and their descendants,...
, while storing data in another medium such as a USB thumb drive, Secure Digital card
Secure Digital card
Secure Digital is a non-volatile memory card format developed by the SD Card Association for use in portable devices. The SD technology is used by more than 400 brands across dozens of product categories and more than 8,000 models, and is considered the de-facto industry standard.Secure Digital...
, or a shared drive on a computer network. Emulators can also be used as a higher-performance replacement for mechanical floppy disk drives.
Emulation process
A typical floppy disk controller sends an MFMModified Frequency Modulation
Modified Frequency Modulation, commonly MFM, is a line coding scheme used to encode the actual data-bits on most floppy disk formats, hardware examples include Amiga, most CP/M machines as well as IBM PC compatibles. Early hard disk drives also used this coding.MFM is a modification to the original...
/ FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
/ GCR
Group Code Recording
In computer science, group code recording refers to several distinct but related encoding methods for magnetic media. The first, used in 6250 cpi magnetic tape, is an error-correcting code combined with a run length limited encoding scheme...
encoded signal to the drive to write data, and expects a similar signal returned when reading the drive. On a write, a hardware PLL or a software-based filter component undoes the encoding, and stores the sector data as logically written by the host. An inverse mechanism translates the stored data back into an encoded signal when the data is read. Noisy raw data signals are filtered and cleaned up before conversion.
Most FDC interfaces do not directly address tracks, rather provide "step-in" and "step-out" pulses. Those, and the current sector number virtually rotating under the emulated read/write head, are tracked by the emulator in order to determine which sector is to be accessed.
Because the interface to the floppy drive is very low-level, emulators must maintain the approximate timing of floppy disk operations. This may require the emulator to provide buffering, with some delay in updating the permanent storage.
The emulator saves the data written to the floppy in either local storage (stand-alone emulators), or in a remote storage device or data exchange module (stateless emulators).
Data exchange
The floppy disk emulator can provide other systems access to the data on the emulated floppy in a number of ways:- Direct access to some dedicated disk partitioningDisk partitioningDisk partitioning is the act of dividing a hard disk drive into multiple logical storage units referred to as partitions, to treat one physical disk drive as if it were multiple disks. Partitions are also termed "slices" for operating systems based on BSD, Solaris or GNU Hurd...
(e.g.: a 1.44Mb partition on a USB key) - Floppy file system translation (e.g.: FAT12 floppy ↔ USB key folder)
- ISO floppy disk imageDisk imageA disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drive, floppy disk, CD/DVD/BD, or USB flash drive, although an image of an optical disc may be referred to as an optical disc image...
s (e.g.: raw floppy ↔ .iso USB key file)
Direct access and ISO image implementations can also emulate system / non-standard floppies, whose file system can't be simply translated.
ISO image implementation can also be coupled with a virtual drive
Virtual drive
A virtual drive in computing is a device that to the operating system appears to be an ordinary physical disk drive, with disc images substituted for disc reading hardware through the use of software called a disk emulator...
to seamlessly emulate floppy drives on a computer.
Some devices can store multiple floppy images, and provide a mechanism to select which emulated floppy is mounted on the emulated drive.