XEX Loader for SIDE and SIDE2

After developing a new main BIOS and PBI BIOS for Ultimate 1MB and Incognito, I decided to write a completely new XEX loader. Presented here is the stand-alone (not requiring U1MB) ROM version of the resulting loader for the SIDE/SIDE2 cartridge. Several features are new to the revised loader; others simply build on the functionality of the original. As of version 4.2, the SIDE Loader shares the newer UI design found in the SIDE3 Loader. Features offered include:

  • Fast and powerful recursive search facility capable of scanning thousands of files and folders on FAT16 and FAT32 volumes
  • Automatic recall of the last accessed folder on the last accessed FAT partition
  • High-speed XEX loading
  • Handling of up to fourteen multiple FAT partitions
  • Redesigned sixteen-line directory display
  • The ability to load BASIC programs
  • FAT loader capable of loading files as low as $0A80
  • CIO FAT file system driver allowing read access to the host volume from XEX programs
  • Full path support in CIO FAT file system and in MAP files
  • Handling of large (more than 250 files) folders
  • Reverse lookup of a mounted ATR or APT partition


You can download the latest version (4.2) of the loader for SIDE and SIDE2 via the link below. The archive contains the stand-alone loader, SDX ROMs, complete ROMs (SDX and loader), as well as ROMs containing ebiguy’s patched OSS language carts (Action!, BASIC XL, BASIC XE, and MAC/65).

SIDE/SIDE2 Loader 4.2 and SDX ROMs (January 2023)


The ZIP contains ATR-based flashers (using a modified version of the SDX flasher) for SIDE and SIDE2. Boot the ATR which corresponds to your hardware, being careful not to flash an original SIDE cartridge on an Ultimate 1MB equipped machine (U1MB flash corruption can occur). SIDE2 does not conflict with U1MB, so may be updated safely on Ultimate equipped machines.

Loader Quick Reference


See the XEX Loader section in the U1MB/Incognito firmware manual for details of how to use the new loader.

Previous Versions

Licensing and Donations

While the firmware is free at the point of delivery for personal use, if it is to be included on commercially sold devices, the firmware is subject to a licensing fee which should be arranged with the author in advance. Developers interested in customised versions of the firmware tailored to their particular hardware should contact the author.

In light of the fact that firmware licensing revenue is modest and that updates are offered for free to the end user, donations are welcomed and appreciated. Indeed, it has been my mission to facilitate easy and safe firmware updates, and regular in-the-field upgrades are encouraged to ensure that devices remain up to date and bug fixes are delivered in a timely manner.

Thank you!

Tutorial Videos