Update the Firmware of Your Ultimate 1MB Upgrade for Atari 8-Bit Computers (5-10 mins)

Task: Update the Firmware of Your Ultimate 1MB Upgrade for Atari 8-Bit Computers

Needed: Ultimate 1MB, Web Browser, SIO2PC or SIDE Cartridge

Time: 5-10 mins


The Ultimate 1MB upgrade for Atari 8-bit computers is one of the most useful modern mods you can do. I have previously posted about the features and installation instructions for this amazing device. FlashJazzCat recently developed and released a firmware update (version 4.0) for the U1MB. The list of new features taken from his web page include:

  • Completely redesigned, larger plugins supporting more hardware
  • Redesigned loader UI displaying more filenames on the screen
  • New ‘modal’ controls allow greater interaction in the setup menu
  • Software compatibility further improved
  • Support for SIDE3, Sophia 2 and PokeyMAX added

A complete list of new features can be found on page 8 of the firmware manual. This is a nice update and it is super easy to install or flash the new firmware. It shouldn’t take more than about five or ten minutes.


First, download the new firmware files (.zip).

Second, navigate your browser to the firmware manual (PDF). The instructions are very clear and easy. Instructions for updating using SIO2PC can be found on page 10. This is what I used. Instructions for using the SIDE loader can be found on page 11.

Note that you should choose U1MBS3FW.ROM from the list of ROMs at the UFLASH.XEX step if you want make and use Atari Partition Table (APT) hard disk partitions on SD cards for use through the SIDE3 loader.


FlashJazzCat has some nice videos on the web page (scroll to bottom) which are helpful to watch. Highly recommended.

Special thanks to FJC for all his work on this and many other projects for the Atari. I sent him $20 today to show my appreciation. You can donate to the cause via PayPal.