The 1541 Ultimate is capable of running both CP/M and GEOS.[7]
In 2010, the 1541 Ultimate II was developed. 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 sourceGPLv3license,[12] allowing hobbyists and others to freely modify all aspects of its functionality, including the FPGA-emulated hardware.
The 1541 Ultimate has an option for on-board Ethernet, while the 1541 Ultimate II supports Ethernet via a compatible USB to Ethernet adapter.[2]
Besides being useful to retrocomputing hobbyists,[4] it has also found use in educational laboratory settings.[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.
^Loguidice, Bill; Barton, Matt (2014). Vintage game consoles : an inside look at Apple, Atari, Commodore, Nintendo, and the greatest gaming platforms of all time. Focal Press. p. 117. ISBN978-0-415-85600-3.