This is a snapshot of the documentation for the Ultimate 64 Data Stream as of May 14th, 2020.  Here is a web link to the original source.

Changelog:

• Sprite Collisions.
• Illegal graphics fetches.
• Sprite DMA timing.
• Nuvie Player.
• NMI handling improved in 6502.
• Illegal reads when BA=0 masked out (“PLA” issue)
• Added debounce on Restore Key.
• KCS power cart fixed (sprite graphics error)
• HDMI/DVI Compatibility.

.. and there are many improvements not present in the changelog.

Ultimate 64 firmware v1.06:

• SpeedDOS Parallel Cable (needs e.g. DolpinDOS roms)
• Interface type: Ultimate Menu picture overlay (HDMI-only)
• USB keyboard support. Like earlier firmware, press scroll/lock to enter/exit the Ultimate menu.
• Replacement of Charrom and BAISC

Note for the Ultimate 64:You will need a kernel, basic and character rom after the upgrade. These roms are not included in the update. These roms are distributed with vice-emu, but you can also find them on zimmermans.net.

For instance, you could use these roms: 901225-01.bin (char), 901226.bin (basic) and 901227-03.bin (kernal). Roms with the .rom extension should also work.

Apparently the version numbers are hex and not decimal.

Differences with previous official release V1.06

• SID has been improved quite a bit.
  • The internal SID is now consistently referenced as "UltiSID", to avoid confusion with other SID products.
  • Various bugs, like the phase of the filters, and the routing of Voice 3 when the VOICE3OFF bit was set have been corrected.
  • A number of SID filter curves have now been implemented and can now be chosen from the configuration menu.
  • The resonance can be changed to two different settings.
  • Combined waveforms can now be selected between 6581 and 8580.
  • Internal bus charge in the SID is now emulated.
• The 6502 core has been improved. All 'stable' illegal instructions are now fully operational:
  • SLO $07 $17 $03 $13 $0F $1F $1B
  • RLA $27 $37 $23 $33 $2F $3F $3B
  • SRE $47 $57 $43 $53 $4F $5F $5B
  • RRA $67 $77 $63 $73 $6F $7F $7B
  • SAX $87 $97 $83 $8F
  • LAX $A7 $B7 $A3 $B3 $AF
  • DCP $C7 $D7 $C3 $D3 $CF $DF $DB
  • ISC $E7 $F7 $E3 $F3 $EF $FF $FB
  • ANC $0B
  • ANC $2B
  • ALR $4B
  • ARR $6B (including decimal mode!)
  • SBX $CB
  • SBC $EB
  • LAS $BB
  • LAX $AB is stable with constant 00.
• U64 settings are now restored when the machine resets. This resets the SID settings after using Auto Config + internal SID player.

Differences with previous release V1.0B

• Based on Ultimate-II+ firmware Version 3.4
• NTSC mode has been added. The switch can be found in the U64 Specific Settings menu
• Added rudimentary support for USB Floppy disks (not completely done yet; as removal of floppy is not yet detected)
• USB problems with low/full speed devices fixed; no more bus hang-ups in these cases. (No full HID support just yet..)
• VIC collision problem fixed.
• Improved 1541 compatibility; weak bit areas and floppy speed zones are now properly supported.
• Various improvements 'under the hood'

Differences with previous release V1.10

• Based on the Ultimate-II+ firmware Version 3.4c
• NTSC mode has been fixed, from 262 lines to 263 lines per frame.
• SID autoconfig: If there is just one SID, give it the full address range.
• Speaker volume setting added for U64.
• Various fixes in the VIC sprite generator. This fixes many demos.
• Preparations added for Elite version of the U64 board
• Adjusted analog colors, thanks to Matt Barszcz
• Fixed sprite collision register timing.
• Fixed line 137 to 000 rollover. This fixes Lunatico three layer scroller
• Added LED controls for the two Case LEDs
• Fixed tape record to tap file
• Fixed various CIA issues. This fixed the Expert Cart unfreeze problem. Thanks to David Horrocks
• Refined IRQ timing of the 6502 CPU core.
• Added AC generator to support UserPort cable
• Fixed the order of Flash images, to make SS5 NTSC and TAR NTSC work.
• Fixed RES bit in $D016, should be writable. Thanks to David Horrocks

Changes to the application, 3.4c, compared to previous 3.4:

• Fixing homedirectory function. Added possibility to use wildcards.
• Fixed file extensions. Makes songlengths load again.
• 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

Differences with previous release V1.18

• Based on the Ultimate-II+ firmware Version 3.5
• Added features:
  • Real time streaming VIC video data over Ethernet
  • Real time streaming audio data over Ethernet
    • Read more about the streams here: Data Streams documentation
  • Added commands on TCP port to enable/disable these streams
  • Added commands to enable/disable emulated drives, over UCI
  • Added possibility to write to D64 images from the menu (e.g. copy PRG files into it).
  • Added DE00 and DF00 ranges as possible options for SID socket decodes
  • Printer emulation now supports color!
• Improvements to VIC:
  • Sprite collision timing solved
  • Sprite to background collision problem solved
  • Sprite expansion timing corrected, also in combination with multicolor
  • Sprite retriggering fixed
  • Border color change timing one adjusted by one pixel
  • Various improvements to pass emufuxx0r tests. (incl. 50-pixel wide sprites)
  • Fixed loading sprite data when VIC is read AEC=1
  • Sprite timing fixed for NTSC
• Improvements to CPU:
  • ANE (B) made to work.
  • Implemented SHA, SHS, SHX, SHY and LAX #imm
  • CPU PIO register floating inputs fixed.
• Improvements to SID:
  • Improvements to ADSR envelope generator (fixes missing notes in e.g. Hawkeye 2018)
  • More realistic values for SID filter resonance
  • Added volume control for the SID digis
  • LowPass boost in sid mixer.
  • Improved anti-aliasing on resample filter in PAL mode
• Improvements on 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
• Other machine fixes:
  • U64 speaker volume fix.
• Other bug fixes
  • Another bug in the network stack that caused stack corruption and random crash
  • 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

Thanks to:

• David Horrocks for very useful input about VIC sprite handling and custom test programs
• Rene Garcia for this addition of color to the printer emulation
• Wilfred Bos for his improvements to the SID (and now MUS) player
• Scott Hutter for added UCI commands
• Martijn Wieland for his U64_Streamer PC application Download here: https://www.tsb.space/projects/u64-streamer/
• Chris Verheijen for his critical ear on UltiSID.

Differences with previous release V1.20

• Based on the Ultimate-II+ firmware Version 3.5a
• Fixed UltiSid reset; should zero all registers to silence it
• Fixed debug register for regression testing
• Fixed directories that match file type extensions

• This is the factory image of the latest production, with support for 1.4 board revision.
• Support for Super Games cartridge.
• Fixed KCS cart at boot time.
• Swapped audio channels, thanks Siegried.
• Improved cartridge timing which corrects the ARMSID detection.

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

Firmware for the U64 / U64E, version 1.34 - Dated: 2020-06-21

Added features since 1.28

• Turbo Mode... The 6510 CPU can now be run faster than 1 MHz.
• Support for Nordic Power cartridge
• Faster application processor for smoother file browsing experience
• Significant lower noise floor when using real SIDs
• From MarkusC64: For Geos 64 - Download D41, D71, D81 and DNP files directly from the file browser into a RAMDISK of the same type.
• From MarkusC64: For Geos 64 - Save RAMDISK to USB in the appropriate format, directly from the file browser
• Added freeze function with USB menu (F11 key)

See details on next page for additional information.

This is not the current version.  As of October 31st, 2021, the current version is v3.10a / Core v1.41

Changes since official release (3.9 / 1.37)

Added features:
- Hardware emulation of 1571 and 1581 drives (U2+ / U64 only)
- MFM support on 1571, with enhanced G71 format to store MFM tracks
- Added audio samples for insert / remove floppy disk
- Added second drive sound to speaker output
- Possiblity to use your own drive sound samples
- Custom U64 palettes
- SystemInfo Page, showing drive, cartridge and storage status
- Flash Disk, to store drive roms, sounds, cartridges and such
- Cartridges are now always CRT files. Selected by filename in the config
- Cartridge compatibility check and reporting
- GMOD2 support, including EEPROM (U2+ / U64 only)
- Zaxxon Cartridge support
- Implemented writing CVT files back to a disk image (enables copying CVT files across disks.)

Changes in 3.10a, compared to 3.10

Fixes:

• [Issue-246] Fixed: Virtual Printer crashes when file cannot be created.
• [Issue-234] Deleting last item in directory makes selection invisible
• [Issue-236] Confirmation modal asking a question only gives 'OK' instead of 'Yes/No'.
• [Issue-R17] Added mapping of ESC key to RUN/STOP.
• [Facebook Request] Added: Leave menu on mount (can be selected per drive)
• [Facebook Bug Report]: Allow Maverick (and others?) to write wrong sector headers on MFM tracks.
• [Facebook Bug Report]: Unable to select GeoRAM. Is now a mode of the RAM Expansion Unit.
• [Facebook Bug Report]: Fixed color palette not loaded at boot (U64 only).
• [Facebook Bug Report]: Fixed USB sticks not recognized
• [Messenger Report]: Improvements to palette file read. Rejects faulty files. Fixes hang-up
• [Messenger Report]: Fixes 'Create DNP' when run from Telnet. Turned out to be a stack overflow.
• [Email Discussion]: Adds EEPROM segment to GMOD2 when it is missing in the CRT file

This is a snapshot of the documentation for the lightweight modem emulation added to the Ultimate 64 firmware starting with version 3.7.  Here is a link to the website this was pulled from.

Gideon (and many helpers) have released Firmware 3.11 / Core 1.43 (Dated 2023-12-28) for the Ultimate 64, 1541 Ultimate-II, 1541 Ultimate-II+ and 1541 Ultimate-II+L.  Here's the changes announcement:

- See the detailed description for Changes in 3.11, compared to 3.10i/j

Please visit the Ultimate 64 Official Firmware page if you'd like to make a donation to this great project!

Latest firmware for the Ultimate 64 / Ultimate64E, version 1.24 - Dated: 2019-10-13

Note: See long description for full details