1541 Ultimate

The unit is developed by Gideon Zweijtzer and is a cartridge that can emulate other cartridges such as the Commodore REU, Action Replay, The Final Cartridge III, Super Snapshot V5, Retro Replay or TurboAss with Codenet-support, and an almost fully compatible[2] (including JiffyDOS support[3] FPGA-cloned Commodore 1541 (including 1541, 1541C, and 1541 II models[4]) floppy disk unit that can use Commodore 64-compatible files like .D64/.G64 disc images or .PRG files via a SD card reader.

The Ultimate II is about 30% smaller than the 1541 Ultimate, comes in a plastic case,[8] and adds support for dual SIDs (plus a SID/MOD player),[9] a USB host controller, tape emulation via a tape adapter[10] (though use with a Commodore 128D requires modification[11]), a real-time clock (for accurate file date and time), and the SD card slot is replaced by a microSD[broken anchor] card slot.

[2] In addition, all firmware and VHDL code for the Ultimate II is available under an open source GPLv3 license,[12] allowing hobbyists and others to freely modify all aspects of its functionality, including the FPGA-emulated hardware.

[13] In 2017 the Ultimate II+ was released with the following feature differentiation from the II: Removal of the MicroSD slot, More USB ports, Integrated Ethernet, Dual Flash, Integrated Speaker, External power supply connector with auto-switch over circuit, Improved power supply circuits, and a slightly bigger and faster FPGA, as to control the new features.

[14] The II and II+ share a firmware image and the software features are substantially similar.