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Floppies

Snow supports 2 or 3 floppy drives, depending on the model you are emulating. The following drives are available, per model:

  • Macintosh 128K/512K: 2 400K drives
  • Macintosh 512Ke: 2 800K drives
  • Macintosh Plus: 2 800K drives
  • Macintosh SE (non-FDHD): 3 800K drives
  • Macintosh SE (FDHD): 3 1.44MB SuperDrives
  • Macintosh Classic: 2 1.44MB SuperDrives
  • Macintosh II (non-FDHD): 2 800K drives
  • Macintosh II (FDHD): 2 1.44MB SuperDrives

PC floppies can be used in the models with SuperDrives, provided you have the 'PC Exchange' extension installed within the emulated system.

Supported image types

Snow supports sector, bitstream and flux image files. Raw flux (e.g. A2R) is also supported, but since these images are not ment for emulator use, it is recommended to convert them to resolved flux or bitstream (if flux accuracy is not required) first.

Writing to flux images is (currently) not supported, these will always be mounted as write-protected.

Snow supports the following image file formats for reading:

  • Apple DiskCopy 4.2 (sector-based)
  • Apple Disk Archive / Retrieval Tool ('DART') (sector-based)
  • Applesauce A2R 2.x and 3.x (raw flux)
  • Applesauce MOOF (bitstream and flux)
  • PCE Flux Image (PFI, flux)
  • PCE Raw Image (PRI, bitstream)
  • Raw images (sector-based)
  • Any format (Mac 1.44MB or PC) supported by Fluxfox

Snow supports saving images to Applesauce MOOF format.

Loading a floppy image

To load a floppy image, go to the 'Drives' menu, to the drive you want to use, and select 'Load image' to browse to the image you want to load.

In the image browser you can view the metadata for the selected image on the right side. To mount an image as write-protected, check the 'Mount write-protected' box. For writable mounts, see Automatic writeback below for how and when changes are written to the disk image.

You can also mount an empty (400K/800K only currently) floppy which you can format and write to by selecting 'Insert blank 400K/800K floppy'.

Ejecting floppies

Floppies should preferably be ejected gracefully through the emulated operating system. To do this, drag the floppy icon on the desktop to the trash.

If your emulated system ejected your floppy and you want to re-insert it including any changes that were made, you can click 'Re-insert last ejected floppy' in the menu for that drive.

Note: if you do not use 'Re-insert last ejected floppy' but instead load the original image after the OS has written to it, the OS will not recognize it as the same floppy!

To forcibly eject a floppy, use the 'Force eject' menu item. This is equivalent to using a paperclip to forcibly eject a floppy on real hardware.

Writing to floppies

When a floppy is written to, the icon in the menu bar will change:

  • save indicates the floppy has not been written to.
  • save_as indicates the floppy was written to since it was mounted.
  • autorenew indicates automatic writeback is enabled for the floppy.

To save a floppy including any changes, use the 'Save image...' item. If the floppy was ejected, you can use 'Save last ejected image...' to save the image from before the floppy was ejected, including changes.

Floppy images are always saved in MOOF format.

Automatic writeback

Snow can also write changes back to a floppy image's source file automatically, as the emulated system writes to it. With writeback enabled for a drive, you do not need to remember 'Save image...' - the source file is automatically saved.

Writeback is only supported for MOOF images, since MOOF is the only format Snow can write. For other formats, Snow can offer to convert the image to a sibling MOOF on load (see Behavior on floppy load below).

Enabling writeback for a drive

When writeback is on for a drive, the floppy icon in the menubar shows autorenew. You can toggle writeback for the currently loaded image at any time via the 'Auto-save changes (writeback)' checkbox in the drive's submenu under 'Drives'. The option is disabled when the loaded image is not a MOOF.

Behavior on floppy load

When loading a floppy, Snow may prompt you before the image is inserted:

  • A sibling MOOF exists. If you load a non-MOOF image and a .moof file with the same filename exists alongside it, Snow asks whether to load the MOOF file instead.
  • The image can be converted to MOOF. If the image format does not support writeback but the image can be converted to MOOF (sector or bitstream images, but not flux-only images), Snow offers to write a sibling .moof and load that. The original file is left untouched.
  • Enable writeback? Once the loaded image supports writeback, Snow asks whether to enable writeback for this image.

The default behavior for each prompt is configurable under 'Options > Floppy':

  • Writeback (Ask each time / Always enable / Never enable) - what Snow does when a writeback-capable image is loaded.
  • Convert to MOOF (Ask each time / Always convert / Never convert) - whether to convert non-MOOF images to a sibling MOOF on load.

Each prompt has a 'Remember my choice' option that updates the corresponding setting.

Backups

Writeback overwrites the source file. To make it easy to revert, enable 'Options > Floppy > Back up floppy image before enabling writeback'. With this on, Snow copies the image to a timestamped sibling in the same directory just before writeback is enabled for it, e.g. MyDisk-bak 2026-05-14 130700.moof. The backup is taken once per writeback activation, not on every write.