1541 Ultimate

Technical Info
ROM	2 MB flash
RAM	32.5 MB (first batch 16MB)
Hardware features	3 Buttons - Freeze, Reset and 1541U Freeze
Manual	PDF: 28 pages from 1541ultimate.net; PDF: 2 pages scan of suplied documentation sheet;
CRT ID	None
Programming	See 1541ultimate.net

	The cartridge described in this article is under constant active development - for recent news and data please check: 1541ultimate.net

1541U is one of the ultimate cartridges for the C64 and regular checks at 1541ultimate.net are a strict requirement for any C64 cartridge lover. Since the 1541U emulates a range of freezer cartridges and allows re-flashing them it is a perfect platform for testing ROMs on the real machine. Cartridge emulation is pretty good and should suit most requirements. This emulation also made the 1541u enter the charts here. There are some problems left as with any other hardware but since this baby can be updated and firmware is publicly available we see a bright future for it.

Following info mostly from the 1541Ultimate Website:

Features

The following are the features of the FPGA core, for hardware features see below. Not all features may be available in all versions of the firmware and/or hardware!

Full emulation of a real Commodore 1541 diskdrive.
- Uses .D64 files stored on SD card
- Supports .G64 files as well (Read only)
- Configurable ID
- Configurable ROM (1541/1541C/1541II or custom)
- RAMBOard memory expansion (16K)
- Drive Noise emulation that works with eg 1541-Music or Drive Composer
Secondary 'IEC-drive' for direct access to FAT filesystem
- Can be used in stand alone mode to mount disks into the emulated 1541.
FAT/FAT32 support, with sub-directories and long filenames
Supports SD V1.1 cards as well as SD V2.0 in High Capacity mode (SDHC)
USB storage device (stick, card reader, and even HD) (1541U-II only)
ISO9660 support with Joliet, for reading .ISO files and access external CD/DVD drives through USB (1541U-II only)

C64 cartridge emulation (also see CRT_ID):
- generic 8k/16k game
- Final Cartridge III
- Action Replay
- Retro Replay
- Super Snapshot
- Ocean
- Epyx FastLoad
- Easyflash
- Magic Desk
- C64GS

Commodore 1750/1764 REU emulation (1541U-plus, 1541U-II)
- Size selectable from 128K up to 16 MB
- Can be combined with Retro Replay and SuperSnapshot compatible roms
Flexible freezer menu
- select, mount, create D64 images, browse disk images
- create new directories, delete files
- Ultra fast DMA load of single file programs (directly from SD / from a .D64 with automount and from a .T64 file)
Configuration screen, with resident settings
Load of last disk on power up
'Stand-alone mode'
- keeps the cartridge port free
- powered through Mini-USB connector
- controlled through buttons and IEC.

RR-NET compatible ethernet (1541U-plus version only, fw 1.x only)
- *NO* Ethernet support yet in stand alone mode!

Dual SID implementation, optionally 8 voices each (1541U-II only)

Built-in SID player; plays SID files on either 'real' SID or emulated SID. (fw 2.4)

PCM output ("Ultimate Audio") (1541U-II only, fw 2.5)
- Up to 7 voices of sampled audio simultaneously accessible through I/O space
- 8- or 16-bit samples, up to 48 kHz sample rate

Built-in copier (fw 2.6)
Command Interface, Accessible module through I/O space that allows direct commands to Ultimate-II (fw 2.6)
Ultimate-II DOS V1.0, I/O space driven direct file access to SD/USB (command target) (fw 2.6)
Kernal replacement function (fw 2.6)

Tape emulation, through 6-pin header on the bottom of the board (requires additional tape connector)
- Load .TAP files to C64
- Capture tape data from a datasette and store it as .TAP file and write .TAP files back to tape, using a Commodore tape deck

Hardware Specifications

The basic hardware platform went through 3 revisions so far:

1541U

Board size: 68 x 100 mm
250k-gate FPGA
Full size 6-pin DIN connector (IEC)
512 kB SRAM
2 MB Flash ROM
16 MB SDRAM
Full size MMC / SD card compatible (Mini/Micro SD possible with adapter)
Stereo audio output
6-pin expansion pin-header for connection to tape port (for C2N emulation), or other future features.

1541U-plus

as above, with the following differences:

32 MB SDRAM (+16MB for REU)
CS8900a ethernet interface

Note: only a small number non-plus boards was produced, all later boards were -plus boards

1541U-II

as above, with the following differences:

Board size: 62 x 84 mm (about 30% smaller than the 1541U)
Sturdy plastic case, enforced with glass fiber
700k-gate FPGA
MicroSD card compatible slot (instead of a full-size SD)
USB host port (supports Mass storage class only)
real-time-clock function, for correct file time and date
ethernet was removed from the hardware

Known Problems

Freezer bug

TODO

Ethernet bug

This is a hardware problem with the -plus version of the 1541U board. When the CS8900a chip is enabled, the RAM under the i/o area can not be accessed correctly, which makes some operations impossible (such as transferring binaries to that area using codenet)

Firmware

1541U

Please note that all these archive contents are available from 1541ultimate.net and newer versions may be available there!

1541u1_2.4a.zip (15 January 2012)
1541u_Firmware_v17beta.rar - includes 1541u-firmware-v17b.pdf and 1541u_v1.7beta.zip (19 August 2010)
1541u_Firmware_v16.rar - includes 1541u-firmware-v16.pdf and 1541u_v1.6.zip
1541u_Firmware_v15.rar - includes 1541u-firmware-v15.pdf and 1541u_v1.5.zip

inofficial

1541-Ultimate-MK1-2.6d.o918r4.zip (7 November 2013) - Obliterator918′s custom 1541 Ultimate Firmware for “mark 1″ units, Version 2.6d.O918.4 Based on Gideon’s SVN revision 131.

1541U-II

Please note that all these archive contents are available from 1541ultimate.net and newer versions may be available there!

1541u2_2.6h.zip (10 August 2013)
1541u2_2.6d.zip (12 February 2013) - this firmware has the "ultimate audio" enabled, but emulates one floppy drive only.
1541u2_2.6.zip (03 February 2013)
1541u2_2.5.zip (03 February 2013)
1541u2_2.5_uaud.zip (03 February 2013) - this firmware has the "ultimate audio" enabled, but emulates one floppy drive only.
1541u2_2.4c.zip (15 January 2012)

Software supporting special features

Listing software that requires one or another special feature only available on "modern" hardware and/or emulators, such as the 1541U, Chameleon or VICE.

16MB REU

bluREU by Crest
NUVIEmaker v0.1e by Crest
Limon REU wave player v2 v3.0d by Data
REU Wave Player v1 (PoC) by groepaz
TAP writer 0.2 > 512 KB TAP writer v1.04 by Enthusi

Note: 16MB REU is also implemented by the Chameleon and can also be emulated by VICE.

Ultimate Audio

"Ultimate Audio" is a custom 7(?) channel PCM output, which is available in 1541U-II Firmwares 2.5+

UltimateAudio simple synth by Freshness
Ultimate Audio MOD Player by Freshness

Notes

codebase64.org has "How the 1541U freezer works" or "Safely freezing the c64" by Gideon Zweijtzer
Commodore Free Issue 35 has an interview with Gideon Zweijtzer
Lotek64 Issue 26 has a german review on the 1541 Ultimate

Wikipedia deleted the page on the 1541 Ultimate (twice actually). Due to "Unambiguous advertising or promotion" the last time. Well - WiPeD 1541 Ultimate tries to recover it.