Disk images

86Box supports a large variety of disk image formats for the emulated storage drives.

Hard disk images

Supported formats:

Format	File extension	Notes
Raw image	Many	Extensions include: .hdd .ima .img
Japanese FDI	.hdi
Extended HDI (HDX)	.hdx
Virtual Hard Disk	.vhd	Fixed, Dynamic and Differencing VHDs are supported through the MiniVHD library.

Hard disk size limits

There are limits to how big of a hard disk an emulated machine can accept. Such limits will vary depending on the machine’s BIOS. The table below lists all important limits applicable to the IDE bus:

Limit	Disk size	Cylinders	Heads	Sectors
20-bit CHS	504 MB	1024	16	63
12-bit cylinder	2015 MB	4095	16	63
ECHS translation	4032 MB	1024	128	63
Revised ECHS	7560 MB	1024	240	63
LBA translation	8064 MB	1024	256	63
16-bit cylinder	32255 MB	65535	16	63
28-bit LBA	131071 MB	65536	16	256

Disk overlay software such as the Vision Systems LBA Enhancer or Ontrack Disk Manager can work around BIOS limits and allow booting of larger IDE hard drives, with the same caveats as using such software on a real machine. The maximum supported disk image size for IDE or SCSI is 131071 MB.

Floppy disk images

Supported formats:

Format	File extension	Notes
Raw image	Many	Extensions include: .bin .dsk .flp .hdm .ima .img .vfd .xdf
86F	.86f	Once loaded, any image can be converted to 86F through the status bar or Media menu.
CopyQM	.cq / .cqm
DiskDupe	.ddi
EZ-DisKlone plus	.fdf
Formatted Disk Image	.fdi	Read only.
HxC MFM	.mfm	Read only.
ImageDisk	.imd
Japanese FDI	.fdi
PCjs JSON	.json	Read only. PCjs 1.0 format only; 2.0 not supported yet.
Teledisk	.td0	Read only.

Floppy disk detection

86Box determines the physical media format (sides, tracks per side, sectors per track, bytes per sector) of a floppy disk image through the following methods:

Image file header data - not applicable for Raw and DiskDupe formats;
DOS BIOS Parameter Block data within the image;
If all else fails, a guess is made based on the image file’s size.

The BIOS Parameter Block detection method may behave incorrectly with non-DOS floppy disks. Installation floppies for UNIX and Linux are common examples of non-DOS disks. Disabling Check BPB is strongly recommended when accessing these, as an inaccurate BPB detection may result in read errors, data corruption and other issues.

Note

When using a Raw image of a non-DOS floppy with Check BPB disabled, make sure the image file is not truncated (smaller than its media size), otherwise incorrect behavior may still occur.

MO / ZIP removable disk images

Supported formats:

Format	File extension	Notes
Raw image	Many	Extensions include: .ima .img
Japanese FDI	.mdi / .zdi	.mdi for MO, .zdi for ZIP.

CD-ROM / DVD-ROM optical disc images

Supported formats:

Format	File extension	Notes
Cue sheet	.cue + .bin	Audio tracks are supported.
ISO	.iso

CD audio

Compact Disc Digital Audio (CDDA) playback through the emulated CD-ROM drives is supported on Cue sheet images. Audio output is enabled on the first CD-ROM drive and muted on subsequent drives by default; individual drives can be muted or unmuted through the status bar or Media menu.

Note

Only raw format (.bin) tracks are supported. Compressed or otherwise encapsulated audio tracks (.wav, .mp3, .ogg, .flac and other formats) are not supported.

Cassette tape images

Supported formats:

Format

File extension

Notes

Raw PCM audio

Many

Extensions include: .pcm .raw

Audio format must be unsigned 8-bit mono.

PCE cassette

.cas

Wave audio

.wav

Audio format must be unsigned 8-bit mono.

PCjr cartridge images

Supported formats:

Format	File extension	Notes
Raw image	Many	Extensions include: .a .b .bin
JRipCart	.jrc

Creating and using disk images

Disk images are a convenient way to transfer files in and out of emulated machines, without the complexity of setting up networking. There are many different command line and GUI tools available for manipulating disk images on each host operating system.

Warning

Before editing or mounting any disk images, make sure they are not in use by any emulated machine that is currently running.

Editing and mounting on Windows

WinImage or PowerISO can be used to create and manipulate disk images on Windows.

VHD images can be natively mounted by double-clicking them on File Explorer, or through the Disk Management tool (diskmgmt.msc): select Action > Attach VHD to mount an image. Eject the drive through File Explorer to unmount. The diskpart command line utility also provides VHD mounting/unmounting functionality.

Mounting on macOS

macOS can natively mount raw hard disk and floppy images formatted as FAT and its variants. Open the image in Finder to mount it, and eject the disk to unmount.

Editing on Linux and macOS

The mtools suite is “a collection of utilities to access MS-DOS disks from GNU and Unix without mounting them”. It can be used to create floppy disk images and directly copy files to them. The mtools package is available on many Linux distributions, as well as macOS Homebrew.

Creating floppy images

The following command will create a 1.44M (1440 KB, double-sided, 18 sectors per track, 80 cylinders) floppy image named floppy.img with a label of LABEL:

mformat -f 1440 -v LABEL -C -i floppy.img ::

The -f option specifies the format of the floppy being created. The command can be adjusted for format, label, and image name as needed. Refer to the mtools documentation for a full list of supported formats.

Copying files to floppy images

The following command will copy file1 and file2 to the floppy image floppy.img:

mcopy -i floppy.img file1 file2 ::

Wildcards are also supported with mcopy.

Note

The :: is required to let mtools know there are no more files to copy or arguments to process.

Mounting on Linux

Linux can natively mount raw disk images (floppy or hard disk) of most types (FAT and NTFS included). The easiest path is to use losetup so that partitions can be properly recognized. Floppies are not normally partitioned, and you can use mount directly.

All following commands must be run as root:

losetup -fP /path/to/86box/hdd
losetup                         # to verify which loopback device was set up.
                                # Assuming /dev/loop0 was selected:
mount /dev/loop0p1 /mnt         # Mount the first partition at /mnt

Disk images should at least be unmounted before running 86Box again, and preferably detached too:

umount /mnt
losetup -d /dev/loop0

Partitionless media can be mounted directly:

mount /path/to/86box/fdd /mnt

VHD images may be mounted via qemu-nbd:

modprobe nbd max_part=16
qemu-nbd -f vpc -c /dev/nbd0 /path/to/86box/hdd
mount /dev/nbd0p1 /mnt
  # After doing some work...
umount /mnt
qemu-nbd -d /dev/nbd0