Commodore 1541-II Floppy Drive Hong Kong Rev 7

The Commodore 1541 Floppy Drive (AKA VIC-1541 / AKA CBM 1541) is a single sided, 5 1/4" floppy disc drive released for use with the Commodore 64 which followed in the footsteps of the 1540 released for the VIC-20.

After numerous reliability issues in 1986 it was updated to the 1541C and matched the C64C in off-white colour.
the 1541C was only slightly more reliable than its predecessor.

In 1988 the 1541C was replaced by the 1541-II, a greatly reduced form factor drive, most notably due to its external power supply VS the internal PSU set up of previous models. Although redesigned, the 1541-II continued to make use of the lever drive release found to be reliable in the second and subsequent releases of the 1541.

Like the 1541/1541C the 1541-II Floppy Drive did not have a sector hole sensor and so was 'soft sectored'. This meant that it was easy for users to cut out a small, square hole on the other edge of a floppy disc to allow both sides to be used. Many cheap, third party 'disc double-siders' (basically a square hold punch that aligned with the disc edge) were released for doing just this.

Each disc side technically had 170kBytes of capacity but the onboard operating system, 'CBM DOS 2.6', needed to allocate a small share for itself. The 170kByte capacity is broken down into 683 sectors on 35 tracks with each of the sectors holding 256Bytes.

CBM DOS 2.6 used a BAM ('Block Allocation Map') and one track was used for that. On top of that, out of each physical sector two Bytes were set aside as a 'block pointer' to point to the next physical track and sector. So in actual fact, a logical block of 256Bytes only held 254. This meant that after formatting almost 165kBytes out of the initial 170kBytes was available for use.

While the drive had been redesigned, it was still slow but to its credit it was much quieter than the 1541/1541C models. However, the drive's main failing point was its new, external power supply brick which was totally encased in non-heat dissipating resin and was completely unserviceable.

If you ever had one of these drives  that started to load a program and then would just stop loading but the disc kept on spinning it was probably the power brick that was at fault and not the drive.

Common Commands:

LOAD"$",8 (loads the directory of the disc to BASIC RAM and displays it on screen)
LOAD"*",8,1 (loads the first program on the disc OR the last program loaded)
LOAD"PROGRAM NAME",8,1

In these examples ,8 states which device to use and ,1 indicates that the program should not be loaded into BASIC RAM but to the memory address specified by the program's header. The 1 usually indicates a machine code / machine language program.

Changing Drive Number on the Hardware

This was done most commonly to allow more than one drive to be chained to the same Commodore 64.

On the rear of the more recent drives are two little paddle switches that were set in the up position by defaul designating the drive as device 8.

Left paddle down with right paddle up = Device 9
Right paddle down with left paddle up = Device 10
Both paddles down = Device 11

Commodore 1541-II Floppy Drive Commodore 1541 II Floppy Drive
Commodore 1541-II Floppy Drive Motherboard Commodore 1541-II Floppy Drive PCB
Commodore 1541-II Floppy Drive Head Commodore 1541-II Floppy Drive Motor Commodore 1541-II Floppy Drive Manual
Commodore 1541-II Floppy Drive Power Supply Commodore 1541-II Floppy Drive Power Pack        
 
Unit pictured has been sold and its location is unknown.