However I've a little doubt: I didn't find any mention about what jumper for what unit: no jumper=8, j1=9, j2=10, j1+12=11? boooooh....
And should the jumper be set conforming the 1541 unit number? Or with these jumpers only I can address it to the choosed unit number, disregarding the original 1541 setting ?
Here is some info from a 1541 manual:
9. CHANGING THE DISK DRIVE DEVICE NUMBER Software Method
The device number is selected by the drive by looking at a hardware
jumper on the board and writing the number based on that jumper in a section
of its RAM. Once operation is underway, it is easy to write over the previous device number with a new one.
FORMAT FOR CHANGING DEVICE NUMBER:
PRlNT# file#, "M-W:" CHR$(119) CHR$(O)CHR$(2) CHR$(address+32) CHR$(address+64)
EXAMPLE OF CHANGING DEVICE NUMBER:
PRINT# 15, "M-W:" CHR$(l19) CHR$(O)CHR$(2) CHR$(9+32) CHR$(9+64) PRlNT# Q, "M-W:" CHR$(119) CHR$(O)CHR$(2) CHR$(R+32) CHR$(R+64)
If you have more than one drive, it's sensible to change the address through hardware (see below). If you must, the procedure is easy. Just plug in the drives one at a time, and change their numbers to the desired new values. That way you won't have any conflicts.
Hardware Method
It's an easy job to permanently change the device number of your drive for use in multiple drive systems. The tools needed is a phillips-head screwdriver and a knife.
STEPS TO CHANGING DEVICE NUMBER ON HARDWARE:
1. Disconnect all cables from drive, including power.
2. Turn drive upside down on a flat, steady surface.
3. Remove 4 screws holding drive box together.
4. Carefully tum drive right side up, and remove case top.
S. Remove 2 screws on side of metal housing.
6. Remove housing.
7. Locate device number jumpers. If facing the front of the drive, it's on the left edge in the middle of the board.
8. Cut either or both of jumpers 1 and 2.
9. Replace housing and 2 screws, and case top and 4 screws.
10. Re-connect cables and power up.
The jumper number is added to the old device number ( 8 )when cut. In other words, jumper 1 adds 1, and jumper 2 adds 2, to the device number. If none are cut, the number is 8, if 1 is cut it goes up to 9, and if only 2 is cut the number is 10. If both I and 2 are cut, the number is 11.