SIDE3 Loader

Following the release of the SIDE3 cartridge in September 2020, development of the SIDE3 Loader has been ongoing, and in July 2021 I embarked on a considerable re-write which resulted in the loader having full read/write access to FAT partitions on the SD card. Not only this, but the UI was enhanced with context menus and drop-down lists, and the loader gained a full complement of file management tools, including a recursive copier and the ability to create new disk images ‘on the fly’. Moreover, the read-only ‘mini FAT DOS’ present in older versions of the loader was replaced by a complete CIO DOS with read/write capability and a command processor.

SIDE3 Beta Loader

The FATFMS disk operating system

Below is a (not exhaustive) overview the features now on offer:

  • Read/write support for up to eight FAT partitions with long filenames
  • 64KB FAT directory buffer allowing the browsing 1,024 files per folder
  • Fast recursive search facility
  • Intuitive context menu system
  • CAR/ROM file loading, ATR mounting, XEX loading
  • Powerful file management tools (recursive file copier, delete, rename, etc)
  • Windows-style cut/copy/paste facilities and keyboard shortcuts
  • PDM audio playback
  • BASIC file loading
  • Built-in FATFMS (an Atari/SpartaDOS FAT workalike with CLI)
  • Autorun facility
  • Bookmarks/favourites
  • Launcher shortcuts and aliases (with hotkey launching)
  • Disk image creation
  • History (remembers your most recently used XEX, ATR and CAR files)
  • Support for SD cards/FAT partitions of up to 128GB
  • Time/date stamping of new and modified files (via real-time clock)
  • Simultaneous HDD/ATR/CAR emulation
  • Bootable, OS-level disk image and HDD support with U1MB when present
  • Limited ATR support without U1MB
  • Remember the last accessed partition, folder, or file

Below is a table which compares the features offered by several popular multi-cart solutions:

SIDE3 Loader Download

Latest build:

SIDE3 Loader 0.69 240123


  • SIMCovox support
  • Fix for cartridge mounting bug
  • UI fixes
  • JED 1.3 update (run with ‘X’ under SpartaDOS X)

See changelog for full details. Note that the latest loader works equally well with JED 1.1 and 1.3.

Important note: while the stand-alone JED update tool has been tested, there is a small risk that if the update fails, the cartridge will be ‘bricked’ and will require recovery by a third-party agent (necessary because the JED file cannot be published). Before updating the JED, please be sure you need to. If the SIDE3 loader already reports JED 1.3 (or you purchased a SIDE 3.1), you already have the latest JED and DO NOT NEED TO UPDATE. If you have JED 1.1 and wish to upgrade without risk, or if you find yourself with bricked cartridge, please get in touch.

Older versions

SIDE3 Loader Beta 0.68 211122

SIDE3 Loader Beta 0.67c 010822

SIDE3 User Manual (Draft)

SIDE3 Loader Manual

Purchase SIDE3

Purchase SIDE3 (Lotharek)

Purchase SIDE3 (RetroLemon)

Purchase SIDE3 (Vintage Computer Center)

Purchase SIDE3 (The Brewing Academy)