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We all know that floppy disks are getting hard to find, and floppy drives are fragile to begin with (especially Commodore's 1541 drive). I know that several companies and parties have released floppy drive replacements that will store floppy disk images on SD cards or USB flash drives, so that we, as users, can avoid having to use floppy disks.

What options are available to today's Commodore users? I'm interested both in general comments about the options available, as well as specific comments about practical usage from users that have experience using specific models of floppy drive replacements.

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    This seems to call for a community wiki answer. – Janka Mar 17 '18 at 19:09
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    @Janka I'm not very familiar with the wiki, but my intention was something that would be a useful reference for future users. – Jim MacKenzie Mar 18 '18 at 0:04
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SD2IEC

SD2IEC is a free software which turns an ATmega644 microcontroller into an emulated VC1541. It attempts a near-complete emulation (I think REL files aren't implemented, but nearly noone ever used them.) The emulation also supports some common fastloaders, most prominently that of The Final Cartridge III.

You store .d64 disk images onto a FAT formatted SD card and can switch between them with toggle buttons or through the special "CD:" DOS command.

The hardware is so simple you can even build it yourself on a breadboard.

1541 Ultimate II Cartridge

The latest incarnation is the 1541 Ultimate II+, and this floppy replacement is also builtin to the newly available Ultimate 64, which is a full C64 motherboard replacement.

Unlike the SD2IEC, the Ultimate II provides a cycle-exact re-implementation of the 1541 floppy drive in an FPGA. As such, it is compatible with any software that reprograms the 1541 hardware through the IEC interface, or which relies on exact hardware timing of the 1541.

Additionally, the Ultimate II provides many other functions like on-screen UI, instant PRG loading (using DMA), 2nd SID, REU, and cartridge emulation, including freezers.

  • If you were running up-to-date Image BBS in 1992 you were using REL files. Just sayin'. – Wildcat Matt May 23 at 19:01
  • Really? I had the impression more sophiscated data handling applications would use USR files or had their own disk format. – Janka May 23 at 19:24
  • Message bases were originally SEQ files, when network support was added to Image, the filetypes changed to REL to better support network synchronization. – Wildcat Matt May 23 at 19:40
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Pi1541

Pi1541 is a real-time, cycle exact, Commodore 1541 disk drive emulator that can run on a Raspberry Pi 3B, 3B+ or 3A+.

It's a Raspberry Pi hat and some specialized software that emulates the 6502 CPU as well as the two 6522 VIAs of a real Commodore 1541 floppy drive. It emulates the whole disk drive so floppy speeders or any other specialized software that runs code inside the floppy drive should work just like on real hardware. This is something that SD2IEC can't do. But if you just want to load and run single file applications or games then SD2IEC will do just fine.

Since version 1.13 Pi1541 can even emulate a Commodore 1581 floppy drive.

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There is a series of cable variants called X1541 collectivly, which have been used as an adapter of the PC parallel port (when PCs still had an parallel port) to the Commodore IEC bus interface.

This made it possible to connect a Commodore disk drive to an IBM PC, and also to emulate a Commodore disk drive by connecting the Commodore computer to the PC.

The IEC bus protocol isn't that complex, and even though parallel ports are not common on modern PCs anymore, it shouldn't be hard to adapt the software to any other sort of hardware that can sense and drive a few lines.

  • Sounds like a good way to repurpose an old PC, too. It might be fun if someone could figure out a way to use the GPIO pins of a Raspberry Pi or similar machine to the same effect. I'm guessing it's just a matter of recoding the interfacing. – Jim MacKenzie Mar 18 '18 at 14:22
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    I used this to connect a real 1571 to my PC and made a backup of my own programs. – Janka Mar 18 '18 at 15:27

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