Anex86 PC98 floppy image
From Just Solve the File Format Problem
Revision as of 00:25, 11 October 2018 by More barbeque (Talk | contribs)
The FDI disk image format for NEC PC-98 disk images seems to originate from the Anex86 PC98 emulator.
FDI File Header
The FDI header is 4096 bytes long, Intel little-endian, and starts with this 32-byte header.
typedef struct {
BYTE dummy[4];
BYTE fddtype[4];
BYTE headersize[4];
BYTE fddsize[4];
BYTE sectorsize[4];
BYTE sectors[4];
BYTE surfaces[4];
BYTE cylinders[4];
} FDIHDR;
The next 4,064 bytes of the header seem to always be pad bytes.
FDI file image contents
The remaining portion of the file is a raw dd-style image of the disk. In the case of an HDM image, you can prepend a 4096-byte header onto the image to turn it into an FDI (see example below).
Examples
For a 1261568-byte "2HD" disk image (like *.HDM format), the header is as follows:
| Field | Value | Comment |
|---|---|---|
| dummy | 0 | |
| fddtype | 144 | Unsure what this value actually means |
| header size | 4096 | Includes the 32-bytes in the header |
| fdd size | 1261568 | |
| sector size | 1024 | |
| sector count | 8 | |
| surfaces | 2 | double-sided disk |
| cylinders | 77 |
