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Hardware Floppy: real Amiga disks in the MEGA65 drive

Your MEGA65 has a 3.5" disk drive built in, and AExp can hand it to the simulated Amiga. Put a genuine Amiga floppy into the slot, and the Amiga 500 inside your MEGA65 reads it and writes it: no image files, no converting on a PC first. Originals boot, copy protection included, and real Amigas read the disks the core writes.

This page is only about the real drive. How drives are configured, and everything about disk images, is on the floppy drives page.

Turning it on

Press Help to open the options menu, go to Drive Settings, and set one of the drives to Hardware Floppy. Out of the box no drive has it: AExp starts with a single disk image drive, df0:, because some games and demos do not cope with more than one drive.

You have two choices. Give df0: itself to the Hardware Floppy, so the one drive is the real one; that is what you want for booting an original disk. Or raise Drives to 2 or 3 and give the Hardware Floppy to one of the extra drives; that is what you want for copying between real disks and disk images.

There is only one mechanism in your MEGA65, so only one Amiga drive can be the Hardware Floppy at a time. Giving it to another drive takes it away from the one that had it.

Changing anything in Drive Settings cold-boots the Amiga, because a real Amiga detects its drives only at power-on. Make your choice, let the machine restart, and then insert your disk. There is nothing to mount and no file to pick: the disk in the slot is the disk in the drive.

Writing: the one thing to be careful about

The Hardware Floppy writes disks as well as reading them, so please read this section before you insert a disk you care about.

The disk's own write-protect tab is the only thing protecting your floppy. There is no switch in the menu, no "are you sure", nothing in AExp that stops a write. If the tab is closed, the simulated Amiga can write, and it will.

On a 3.5" disk the tab is the little sliding shutter in the corner:

  • Hole open: the disk is protected and nothing can be written to it. Use this for anything you care about.
  • Hole closed: the disk can be written.

So the rule for your collection is: originals stay open. Slide the tab open on every game, every old disk and every disk you could not replace before it goes near the slot. Then the drive physically cannot alter it, whatever a program tries.

For writing, use blank disks or ones whose contents you would not miss. Writing real disks is the youngest part of the core.

The Amiga does not check its own writes: nothing on a real Amiga reads a track back to confirm it, so a failed write goes unnoticed until you next read that disk. This is why X-Copy's verify option is worth keeping on, and another reason to keep the tab open on anything irreplaceable.

For everyday saving, formatting and Workbench work, disk images in the other drives remain the easy and safe choice.

Double density only

Amiga floppies are double density (DD), 880 KB formatted. The MEGA65's drive is a PC-style mechanism, and such a mechanism physically cannot read an Amiga high-density (HD) disk. So:

  • DD disks, the normal Amiga kind with one square hole in the corner, work.
  • HD disks, with two square holes and usually marked "HD", do not, and no setting changes that. It is a property of the mechanism, not of AExp.

Almost every Amiga disk ever pressed, duplicated or copied at home is DD, so this rules out very little in practice.

Watching it work

While the options menu is open, the Hardware Floppy line shows what the drive is doing. The line belongs to whichever drive has the Hardware Floppy, so read the df0: below as df1: or df2: if you put it there:

  • df0:Hardware Floppy: idle.
  • df0:HW Floppy: Motor: the motor is spinning, but no data is reaching the Amiga.
  • df0:HW Floppy: Reading: decoded data is streaming into the Amiga.

A write shows as Motor, not Reading: while the Amiga writes, nothing is read back, so no data flows towards it.

This helps when something does not load. If a program waits and the line says Motor, the drive is turning but nothing readable comes back: the disk is blank, unformatted or badly worn. If it says Reading, the disk is being read.

Copy-protected originals

Many Amiga games never shipped as plain AmigaDOS disks. They used custom track formats, their own loaders, and copy protection that depends on how the disk physically behaves: sector timings a copier cannot reproduce, deliberate errors, tracks that only make sense to the game.

Those disks work. One of the most widespread protection schemes on the Amiga was Copylock by Rob Northen Computing, and titles using it (Cannon Fodder, The Chaos Engine, Terminator 2, The New Zealand Story) boot and play from the real disk in the MEGA65's drive. So do custom trackloader formats and demoscene loaders that never used AmigaDOS at all.

Copylock does not just read the disk, it times it: it watches one of Paula's registers while raw data goes past and compares a slightly short sector against a slightly long one. AExp feeds that register with what the real disk is doing, so the check passes.

Protection does not survive copying, which is its purpose. A copier running on the Amiga, such as X-Copy, cannot reproduce a Copylock track, on AExp just as on a real Amiga. Use your originals directly and do not expect a working copy of one.

What to expect from old media

Old disks are fine. Originals from the late 1980s and early 1990s boot directly, including ones their owners described as marginal on real hardware. The core copes with the point on every track where the original duplicator stopped writing, which is where old disks are hardest to read.

Floppies still age. The magnetic coating sheds, and a disk that read perfectly in 1994 may have lost whole tracks since, without any visible damage. If a disk fails, try another one, and if something still looks wrong, please tell us. A disk that reads on a real Amiga but not on AExp is a bug, not a tired floppy.

If the drive knocks and reads nothing after switching on

Rarely, the drive mechanism itself starts up in a bad state: right after you switch the MEGA65 on and insert a disk, the drive knocks for a few seconds and nothing reads, not even a disk that worked yesterday. Ejecting and re-inserting does not help, and neither does resetting the Amiga.

Neither the core nor your disk is at fault. The built-in drive has a small controller of its own, which occasionally starts up in a bad state and resets only with the power. Switch the MEGA65 off and on again, and the drive is back to normal.

Read errors without the knocking are a different matter: see the previous section, and try another disk first.

What you can do with it

Real Amigas read what the core writes: an A500 (OCS, Kickstart 1.3) and an A500+ (ECS, Kickstart 2.0) read back disks the core had written, an A1200 with Kickstart 3.2 read a disk the core had cloned, and a bootable Workbench disk cloned end to end by the core booted on real hardware. Everything below has been done on real hardware.

Most recipes use this three-drive layout. In Drive Settings, set Drives to 3, leave df0: and df1: as Disk Image, and set df2: to Hardware Floppy. Out of the box only df0: exists, so you set this up once. The Amiga cold-boots when you change it, so do it before you load X-Copy or Workbench. See the floppy drives page for mounting disk images.

Whenever a recipe writes to a real disk, the write-protect tab is the only guard: keep it open (protected) on the disk you copy from, and close it only on the disk you mean to overwrite.

Make a real disk from an ADF with X-Copy

  1. Set up the three-drive layout above.
  2. Mount the ADF you want to write in df1:, then the X-Copy ADF in df0:. A disk in df0: boots as soon as it is mounted.
  3. Put a blank disk, or one you do not need, into the MEGA65's drive with its tab closed.
  4. In X-Copy, select df1: as the source and df2: as the target, switch verify on, and start the copy.

With verify on, X-Copy reads every track back and tells you at once if the disk does not take the data. A whole-disk copy of 160 tracks made this way was byte-identical to a known-good reference.

Copy a real disk into an ADF, and back

With the same layout and X-Copy in df0:, mount an ADF you can overwrite in df1: and put the real disk, tab open, into the drive. In X-Copy, copy from df2: to df1: with verify on, and you have the disk as an ADF on your SD card; wait for the drive LED to stay off before you unmount it. To write it to another real disk, insert a blank one with its tab closed and copy from df1: to df2:, again with verify on. Copy-protected tracks do not survive this, as explained above.

X-Copy can also copy through memory with a single drive: choose the Hardware Floppy as both source and target, switch verify on, and swap the disks when X-Copy asks.

Format a disk and work with it in Workbench

Boot Workbench 1.3 from an ADF in df0: with the Hardware Floppy as another drive. Format a real disk in the Hardware Floppy, copy files and programs onto it, and they load and run from it after you switch off and boot again.

Games that save in their own non-DOS format work too: Giana Sisters saved a high score to a real disk, and it was still there after a power cycle.

Getting files off a real disk

You can rescue the contents of a real disk into a disk image with nothing but the Amiga's own tools:

  1. Set up the three-drive layout above.
  2. Mount a Workbench image in df0: and a writable image in df1:; a formatted, empty one is ideal.
  3. Boot Workbench, put your real Amiga disk into the MEGA65's slot with its tab open, and copy across. From the Shell that is something like copy df2: to df1: all, or drag the icons between the two disk windows on the Workbench screen.
  4. Wait until the drive LED has stayed off for a few seconds, so everything is safely written back to the SD card.

The result is an ordinary .adf file on your SD card, holding the contents of a disk that will not last forever. You can back it up, copy it to a PC, and keep using it long after the original has given up.