A floppy disk hardware emulator or semi-virtual diskette (SVD) is a device that emulates a

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, a diskette, or a disk) is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a ...

drive with a solid state or network storage device that is

plug compatible Plug compatible refers to " hardware that is designed to perform exactly like another vendor's product." The term PCM was originally applied to manufacturers who made replacements for IBM peripherals. Later this term was used to refer to IBM-com ...

with the drive it replaces, similar to how

solid-state drive A solid-state drive (SSD) is a type of solid-state storage device that uses integrated circuits to store data persistently. It is sometimes called semiconductor storage device, solid-state device, or solid-state disk. SSDs rely on non- ...

s replace mechanical

hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating hard disk drive platter, pla ...

History

Older models of

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

electronic musical instrument An electronic musical instrument or electrophone is a musical instrument that produces sound using electronics, electronic circuitry. Such an instrument sounds by outputting an electrical, electronic or digital audio signal that ultimately is ...

s and

industrial automation Automation describes a wide range of technologies that reduce human intervention in processes, mainly by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machine ...

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 An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

, software and data to be read and written from and to floppies, forcing users to 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, or 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 A floppy-disk controller (FDC) is a hardware component that directs and controls reading from and writing to a computer's floppy disk drive (FDD). It has evolved from a discrete set of components on one or more circuit boards to a special-purpo ...

, while storing data in another medium such as a USB thumb drive,

Secure Digital card Secure Digital (SD) is a proprietary, non-volatile, flash memory card format developed by the SD Association (SDA). Owing to their compact size, SD cards have been widely adopted in a variety of portable consumer electronics, including digi ...

, or a shared drive on a computer network. Emulators can also be used as a higher-performance replacement for mechanical floppy disk drives. A typical application is the replacement of worn-out floppy disk drives of classic digital musical instruments (

synthesizers A synthesizer (also synthesiser or synth) is an electronic musical instrument that generates audio signals. Synthesizers typically create sounds by generating waveforms through methods including subtractive synthesis, additive synthesis and ...

and samplers) so that they can still be used for music production today.

Emulation process

A typical floppy disk controller sends an MFM / FM /

GCR GCR (or GCRS) may refer to: Science * Galactic cosmic ray, a cosmic ray from outside the Solar System * Geocentric Celestial Reference System, a coordinate system for near-Earth objects like satellites * Geological Conservation Review, a procedu ...

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; instead they 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 partition Disk partitioning or disk slicing is the creation of one or more regions on Computer data storage#Secondary storage, secondary storage, so that each region can be managed separately. These regions are called partitions. It is typically the first ...

(e.g.: a 1.44MB partition on a USB key) * Floppy file system translation (e.g.: FAT12 floppy ↔ USB key folder) * Floppy

disk image A disk image is a snapshot of a storage device's content typically stored in a file on another storage device. Traditionally, a disk image was relatively large because it was a bit-by-bit copy of every storage location of a device (i.e. every ...

s (e.g.: raw floppy ↔ .img/.iso USB key file) ''Direct access'' and ''floppy image'' implementations can also emulate system / non-standard floppies, whose file system can't be simply translated. ''Floppy 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.

References

{{reflist

History

Emulation process

Data exchange

References

See also