This directory contains ROMs of 1540, 1541, 1541C and 1541-II drives.
The ROM checksums are valid. If you add the byte values together (adc data:adc #0), the sum of the $c000-$dfff ROM will be $c0, and the $e000-$ffff ROM will add up to $e0. This applies also to the halves of the 1541-II ROM.


3rd party modifications to the firmware
Schematic diagrams


1540-c000.325302-01.bin 1995-03-02 8192
The ROM chip for $c000-$dfff. This seems to be the same on all models before the 1541-II.
1540-e000.325303-01.bin 1996-06-26 8192
The firmware of an 1540 (the drive that the C64 wouldn't keep up with). The revision number might be something else than -01. A speciality of this chip is the power-up message: 73,CBM DOS V2.6 V170,00,00. Did Commodore want to call the drive V170 first? The ROM checksum is correct. The long-board 1541 had the same hardware as the 1540; this upper ROM was the only difference. The lower ROM was 325302-01 on both drives.
1541-II.251968-03.bin 1986-07-07 16384
1541-II firmware. Released in 1987.
1541-c000.325302-01.bin@ 1995-03-02 8192
The ROM chip for $c000-$dfff. This seems to be the same on all models before the 1541-II.
1541-e000.901229-01.bin 1998-01-20 8192
This is believed to be the first revision of the 1541 firmware. The service manual says that this ROM is for North America and Japan only. According to it, a 901229-02 also exists, but not in North America. 901229-03 is said to be the first version that is usable in Europe.
1541-e000.901229-02.bin 1999-06-28 8192
Second version of the 1541 firmware. Uploaded by Raymond Day <raymondday@hotmail.com>. Two delay loops are shorter than in 901229-03, and the checksum byte at $fee6 has been adjusted accordingly.
1541-e000.901229-03.bin 1996-05-08 8192
The firmware of an old-style 1541 with long board. This ROM has an autobooting feature: if CLK and DATA are held low during bootup, the drive will wait for them to raise, and execute a "&*" command.
1541-e000.901229-05.bin 1995-03-02 8192
The firmware of an old-style 1541 with short board.
1541C-to-1541-II.txt 2003-06-06 11214
A comparison of the 1541C and 1541-II firmware by Wolfgang Moser. The support for the optical "track 0" sensor, which was introduced in the 1541C firmware, was removed in the 1541-II firmware.
1541C.251968-01.bin 1997-09-10 16384
The firmware of an old-style 1541 in white case. This drive was introduced around the same time with the C128 and the 1570, to make it look like the C128 and the 1570, which was also in a white 1541-style case. The C128 was also white. This drive has an optical track 1 sensor, but it won't be used unless the jumper J3 on the board is cut.
The $c000-$dfff part of this chip is identical to the 325302-01 ROM.
1541C.251968-02.bin 1999-08-09 16384
An upgrade ROM for the 1541C. There are patches in both 8k halves.
1541C.251968-02.txt 2001-12-10 1847
Release notes for the 251968-02.

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