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 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, and others simply build on the functionality of the original. They include:

  • Recursive searching of entire directory tree, accomplished by simply typing the first characters of the desired file or folder name
  • High-speed XEX loading
  • Handling of multiple FAT partitions
  • APT partition mounting
  • Easy mounting of multi-disk volumes via MAP files
  • Loading of 8KB ROMs and BASIC programs
  • FAT loader capable of loading files as low as $0A80
  • Optional FAT file system handler allowing read-only access to the host volume via the CIO


You can download the latest version of the loader for SIDE and SIDE2 via the link below. The archive contains stand-alone

SIDE/SIDE2 Loader and SDX ROMs (July 2018)


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.

Also in the ZIP is a copy of the 256KB padded ROM, should you have a RAM expanded machine and wish to use UFLASH to flash the ROM to the ‘External Cart’ section of your SIDE or SIDE2 cartridge.


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

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

Thank you!