Emulate File format

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Emulate files are stored on disk as a file with attributes similar to that of a program file. An emulate file is a sector dump image, comprised of 256-byte sectors, in a format identical to that of a floppy disk. Emulate files were introduced by Myarc with their HFDC system. They may be used in cases where the reference to the disk drive is hard-coded into the program, not allowing to run the program from a hard drive.

The DSR creates a File Descriptor Record for the emulate file which it then uses to track the location of each virtual disk sector.

As the emulate file is essentially a sector dump disk image, it may be directly used in emulators like MESS. Before using it, the TIFILES header must be stripped, but the contents may remain unchanged.

Maximum emulate sector size:

  • HFDC w/TI: 1600 sectors
  • HFDC w/Geneve: 12800 sectors

To accomplish more than 1600 sectors, MDOS calculates sectors per AU as follows:

  • 0-1599 sectors - 1 sector/AU (400MB Max)
  • 1600-3199 sectors - 2 sectors/AU (800MB Max, "quad density")
  • 3200-6399 sectors - 4 sectors/AU (1.6MB Max, "high density")
  • 6400-12799 sectors - 8 sectors/AU (3.2MB max, "ultra-high density")

HFDC DSR cannot exceed 2 sectors/AU. Geneve DSR cannot exceed 8 sectors/AU.