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Category: 1541 Ultimate II
Downloads: 26
d64 floppy0 1541 Ultimate II Audio API Manual

The ‘Ultimate Audio’ feature is a new feature for the 1541 Ultimate-II module. It implements multichannel audio sample playback support from REU memory, and is an exciting addition to the possibilities this cartridge offers. 

13-01-16 English PDF 567.02 KB 542 Download
zip1 1541 Ultimate II Firmware 2.5a

1541 Ultimate II Firmware 2.5a

15-01-16 English Commodore 64 799.77 KB 599 Download
zip2 1541 Ultimate II Firmware v2.4a

1541 Ultimate II Firmware v2.4a

20-01-16 English Commodore 64 794.8 KB 569 Download
zip3 1541 Ultimate II Firmware v2.4c

1541 Ultimate II Firmware v2.4c

15-01-16 English Commodore 64 695.22 KB 555 Download
d64 floppy4 1541 Ultimate II Firmware v2.5

Version 2.5 includes some new features:

  • File viewer.
  • Selectable colors in user interface.

This version also includes some fixes for nasty memory allocation bugs that existed when using USB sticks. Removal of a USB device is now at least a lot safer. Also, some file system bugs were fixed.

13-01-16 English Windows 702.13 KB 531 Download
d64 floppy5 1541 Ultimate II Firmware v2.5+

Version 2.5+ includes some new features:

The ‘plus’ version of 2.5 including a special 7-voice audio engine. This version is based on the same 2.5 with the bugfixes and a special FPGA build can it only supports ONE floppy drive, in favor of extra audio functionality.

13-01-16 English Windows 694.53 KB 520 Download
zip6 1541 Ultimate II Firmware v2.5x

1541 Ultimate II-Firmware v2.5x

15-01-16 English Commodore 64 696.44 KB 566 Download
d64 floppy7 1541 Ultimate II Firmware v2.6

Version 2.6 includes some new features:

  • Disk Copier from real drives to .D64 images
  • Command Interface
  • Ultimate-II DOS V1.0 (command target)
  • Kernal replacement function

... and some important fixes, including:

  • TAP file recorder failed miserably on high latency write devices. Rewritten; should work better now.
  • Drive data timing has improved. Timing is now dependent on the data track itself, not on the speed setting of the VIA. This fixes some protected titles in G64 format.

Release notes:

  • This version does *not* include SID, but it does include the Ultimate Audio module. Different builds may become available upon request.
  • The internal copier is still in beta. It has been tested with some of my drives, but there might be drives out there that won't work. Make sure you have an IEC link from the Ultimate to a real drive to use this function. (No need to have a link to the computer.) There is still no retry mechanism; sectors that failed to read correctly will not be re-read.
  • The Kernal replacement function is critical when it comes to timing. Tested on two machines only. Might not work on C128.

Installation instructions:

  • Unzip the downloaded file into the root of your SD card.
  • Place the SD card in the 1541Ultimate II.
  • Boot your Commodore machine
  • Wait for instructions and remove SD after flashing. Suggestion: remove 'update.bin' from the root of the SD, using the PC or the delete command in the Ultimate.

Command Interface and Ultimate-II DOS

See the documentation of the Command Interface module for knowing how to use it!

See the documentation of the Ultimate-II DOS, to get to know what you can do with the Command Interface in this firmware release.

04-11-16 English Commodore 64 709.29 KB 632 Download
d64 floppy8 1541 Ultimate II Firmware v2.6d

Release notes 2.6d:

  • * Ultimax mode forced now correctly implemented (solves issue with freeze and DMA load)
    * Programmable cartrige emulation timing
    * Some drive emulation enhancements
  • FIXED: Ultimax mode forced now correctly implemented (solves issue with freeze and DMA load)
  • FIXED: Updater now works on C128... (not all C128 issues are fixed)
  • ADDED: Programmable cartrige emulation timing
  • IMPROVED: Some drive emulation enhancements
  • Release notes 2.6c:
  • This version does include SID, but is just single-drive. It does include the Ultimate Audio module. Different builds may become available upon request.
  • FIXED: USB stick present on boot time caused the Ultimate-II to crash when loading a file from SD at initialisation time (kernal rom / drive rom)
  • FIXED: Starting a program with RUN sometimes caused the ultimate to become unresponsive when freezing afterwards.
  • FIXED: Now reads USB sticks with FAT16 format, but without partition table.

See for additional information the download item of V2.6

04-11-16 English Commodore 64 711.14 KB 617 Download
zip9 1541 Ultimate II Firmware v2.6e Dual Drive [unofficial]

1541 Ultimate II Firmware v2.6e Dual Drive [unofficial]

15-01-16 742 KB 521 Download
zip10 1541 Ultimate II Firmware v2.6g

1541 Ultimate II Firmware v2.6g

15-01-16 English Commodore 64 689.11 KB 563 Download
zip11 1541 Ultimate II Firmware v2.6g w/1 drive and SID [unofficial]

1541 Ultimate II Firmware v2.6g w/1 drive and SID [unofficial]

15-01-16 English Commodore 64 716.29 KB 511 Download
d64 floppy12 1541 Ultimate II Firmware v2.6h

Version 2.6h contains some small fixes on top of 2.6d.  This build is a DUAL DRIVE version with NO SID emulation.

  • Release notes 2.6h
  • Timing fixed for C64C
  • Newer version of built-in MOD player
  • Bug fixes regarding USB stick removal
  • Enhancements under the hood for networking support. Network support will be enabled later, is not part of this version!

See for additional information the download item of V2.6d.

04-11-16 English Commodore 64 729.91 KB 595 Download
zip13 1541 Ultimate II Firmware v2.6k w/audio

1541 Ultimate II Firmware v2.6k w/audio

15-01-16 English Commodore 64 716.44 KB 568 Download
zip14 1541 Ultimate II Firmware v2.6k w/dual drive

1541 Ultimate II Firmware v2.6k w/dual drive

15-01-16 English Commodore 64 708.87 KB 542 Download
zip15 1541 Ultimate II Firmware v3.0 Beta 4

1541 Ultimate II Firmware v3.0 Beta 4

15-01-16 English Commodore 64 2.23 MB 570 Download
d64 floppy16 1541 Ultimate II Firmware v3.0 Beta 5

A new version of the firmware for the interface 1541 Ultimate II is released. This version runs only on the 1541 Ultimate II cartridge (new fpga).

Release notes 3.0 beta 5:


  • BUGFIX: Processor’s Data Cache stored result of IO read, causing wrong values to be read from the cache


  • C64 Keyboard scan made a bit slower  (not tested)
  • Fixed configuration drop down
  • Fixed clock settings
  • Mount disk made first option in D64 file type
  • Updated Final 3 cart.

Release notes 3.0 beta 4 (first version released on Facebook):

  • The FPGA platform has gotten an upgrade. There is now a faster RISC processor on board (~10 times faster), and I have re-written the USB host controller, which has become ~50 times faster. The external memory of the FPGA also runs faster, and delivers now also approx. 7 times more bandwidth. With this faster platform, it has become possible to run a multithreaded OS.
  • There is now support for USB2LAN adapters, and 3.0beta4 runs two services: a (raw-)telnet (VT100) server that brings up the menu, and an FTP daemon for basic file transfer.
  • There is now support for reading the directories of D71 and D81 files in the browser.
  • There is a ‘CD’ command in the software IEC, and other improvements have been made to the soft IEC driver.
  • There is now a copy command in the file browser, that works with C=C/C=V (or CTRL-C / CTRL-V). It is not that fast, but for small files it works. You can also copy files from inside a D64/T64 to another location in the file system. The other way around is still under development, but will soon be possible as well.
  • UltiCopy is disabled for now, because it still needs to be ported to the multi-threaded operating system.
11-01-16 English Windows 2.28 MB 711 Download
d64 floppy17 1541 Ultimate II Firmware v3.0 Beta 7

3.0 BETA 7

r297 | gideonz | 2016-04-15 21:27:25 +0200 (Fri, 15 Apr 2016)

Prepared for release 3.0b7
Processor flag error fixed.
Some 6502 opcode testing done. Fixed ADC in decimal mode.

Some fixes:
ISSUE 189: Mount disk is now performed when C64/drive is not frozen
ISSUE 191: Loading a file from within T64 (and D64) could fail at times due to special chars. Fixed
ISSUE 193: Tape grab to TAP file fixed (at least that the option to run it will work)
ISSUE 204: TCP slowdown fixed; bug in USB driver
ISSUE 207: Typo fixed that caused "Save to disk" to fail with a 0 byte file
OTHER: SID file with faulty header now no longer causes Flash corruption
OTHER: Tape play / record functions updated

r276 | soci | 2016-01-17 07:35:38 +0100 (Sun, 17 Jan 2016)

Fix wrong DDRA readback (typo)
The TASM-RR cartridge is not REU compatible
Fix for PB6/7 keyboard freeze bug

22-06-16 English Commodore 64 2.28 MB 619 Download
zip18 1541 Ultimate II Firmware v3.2

** Contains firmware for both 1541 Ultimate II and 1541 Ultimate II+

 Release notes 3.2


  • Completely rewritten SID player, by Wilfred Bos
  • Enhanced version of FC3, by Daniël Mantione
  • Added Tape Index function, as suggested by Tom Roger Skauen
  • Added UCI interface to access the network (TCP/IP and UDP/IP) through Ultimate Command Interface  (documentation pending)
  • Many additions and bug fixes by Henning and Markus, including Home Directory, REU load on startup, EasyFlash write support (manual save), and more.
  • Some enhancements in FTP server
  • Additional bug-fixes.

Installation instructions:

  • Copy unzipped file to USB stick.
  • Put the USB stick in the U2+.
  • For the 1541 Ultimate-II:
    • Navigate to the unzipped file 'update_audio_3.2.u2u' or 'update_dual_drive_3.2.u2u' and select "Run Update"
  • For the Ultimate-II+:
    • Navigate to the update_3.2.u2p file, and select "Run Update".
24-08-18 English Commodore 64 2.66 MB 703 Download
zip19 1541 Ultimate II Firmware v3.4c

1541 Ultimate II Firmware v3.4c

Release Notes

  • Fixing homedirectory function. Added possibility to use wildcards.
  • Fixed file extensions. Makes songlengths load again.
  • Fixed missing SID voices in U2/U2+
  • Significant improvements to the Software IEC module.

  • Updates to SID player:

    • Implemented pause feature (using space bar)
    • Pause will now also mute 2nd and 3rd SID chip
    • Fixed SID version check and SID header relocation
    • Fixed display issue when SID model or clock is unknown
    • Updated version of player and copyright year
01-09-19 English Commodore 64 1.79 MB 421 Download
zip20 1541 Ultimate II Firmware v3.6

General Usability and Compatibility:

  • Added possibility to load / save and reset configuration settings.
  • Added the possibility to have temporary configuration settings.

Improvements to the 6502 CPU for improved 1541 compatibility:

  • Improvements to SID player:
    • Built-in SID player now supports MUS files as well (including stereo tunes) Music files can be found here: http://www.c64music.co.uk/
  • Added support for toggling screen on/off in Sidplayer with S key.
  • Added support for song length in SID header.
  • Fixed correct SID model selection for SIDFX boards.

Various other bug fixes:

  • Copying a file from a container now restores extension.
  • Fixed issue of copying file from .t64 files.
  • Added ‘Enter’ option for .t64 files.
  • User Interface improvements / fixes.
  • Fixed telnet connection – removing header upon connect (fixes random copy actions)
  • Changed default hostname to match target.

Dropped features:

  • Support for the ISO9660 filesystem.
  • The audio variant no longer supports recording TAP files. The dual drive version does.
20-10-19 English Commodore 64 1.81 MB 444 Download
zip21 1541 Ultimate II Firmware v3.7

Added features since 1.24

  • Debug stream over Ethernet, which logs CPU / VIC access real time, also possible to log C64 CPU and 1541 CPU alongside. U64 only.
  • ACIA (MOS 6551) emulation
  • Modem Layer emulation (6551 <-> LAN), supporting both outbound and inbound connections
  • REU load / save commands from UCI, using the preload settings
  • File append mode for Software IEC.
  • Support for SuperGames cartridge
Website external 14-05-20 English Commodore 64 1.79 MB 403 Download
d64 floppy22 1541 Ultimate II Quick Guide (Firmware 2.6k)

This is the quick install / user guide for the 1541 Ultimate II running firmware 2.6k.

26-05-15 English PDF 304.71 KB 587 Download
zip23 D71 - D81 Writer v1.1

A Dutch user by the name of Wiebow (aka WdW) has made a small ultility to write D71 (1571 diskdrive) and D81 (1581 diskdrive) from image file back to the real drive. It uses the 1541 Ultimate II(+) api to do so. The 1541 Ultimate II (+) does not allow you to mount a D71/D81 image, but at least you can write it back to real disk and run it on your C64 and 1571/1581 hardware.

D71-D81 Writer
30-08-18 English Commodore 64 28.71 KB 678 Download
d64 floppy24 Ultimate Audio MOD Player

Freshness released a new program for the 1541 Ultimate. The program can be used for playing audio MOD files with your 1541 Ultimate. The MOD file system was developed by Karsten Obarski in 1987 for tracker software on the Amiga computer.

13-01-16 English Commodore 64 93.94 KB 564 Download
zip25 Ultimate II Command Interface Reference v1.0 NEW

Command Interface Reference v1.0 (2013) by Gideon Zweijtzer - Although the title suggests this is only for the Ultimate II, this document is also valid for the Ultimate II+ and Ultimate 64.  Here is the overview as quoted from the document:

The ‘Ultimate-II command interfacefeature is a new feature for the 1541 Ultimate-II module. It implements a way to communicate to the 1541 Ultimate-II programmatically from the Commodore 64, through the cartridge port I/O registers.

TheUltimate-II command interfaceis the communication layer between the C64 on one side and functional modules of the 1541 Ultimate-II on the other side. Such a functional module takes a command, and returns data and status back to the user program on the C64.

This document was obtained from the 1541 Ultimate official Github repository and should not be considered the most current version.  Please visit the Github project for updates and other related documentation.

19-01-23 English PDF 738.02 KB 36 Download
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