Formatted Disk Image
Encyclopedia
FDI is a file image of a disc created with the Disk2FDI PC
software. It is often used to read Amiga
or C64
discs and other discs formatted in a way that normally can't be read with a PC.
The software uses two methods:
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...
software. It is often used to read Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
or C64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
discs and other discs formatted in a way that normally can't be read with a PC.
The software uses two methods:
- Connect two floppy disk drives to a PC and fill drive-0 with an ordinary PC formatted floppy disc. Drive-1 receives a foreign format disc. Then the software reads as normal from drive-0, but then selects drive-1 instead. It thus bypasses obstacles that would make the floppy controller otherwise refuse the format of the foreign disk. In particular it gets the PLLPhase-locked loopA phase-locked loop or phase lock loop is a control system that generates an output signal whose phase is related to the phase of an input "reference" signal. It is an electronic circuit consisting of a variable frequency oscillator and a phase detector...
to sync.
- Connect one disc drive to the PC via a cable that lets the parallel portParallel portA parallel port is a type of interface found on computers for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port...
interruptInterruptIn computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
pin "Acknowledge" trigger on the read signal. The Index signal is also read on the "Select" line. Using both signals a map of the position of the data per revolution can be built. The PC only needs to make the drive spin and use correct track and head. The reading is done by software exploiting interrupt timings.