The Commodore 1581 is a 3½-inch double-sided double-density floppy disk drive that was released by Commodore Business Machines (CBM) in 1987, primarily for its C64 and C128 home/personal computers.

The drive stores 800 kilobytes using an MFM encoding but formats different from the MS-DOS (720 kB), Amiga (880 kB), and Mac Plus (800 kB) formats.

With special software it’s possible to read C1581 disks on an x86 PC system, and likewise, read MS-DOS and other formats of disks in the C1581 (using Big Blue Reader), provided that the PC or other floppy handles the “720 kB” size format.

This capability was most frequently used to read MS-DOS disks. The drive was released in the summer of 1987 and quickly became popular with bulletin board system (BBS) operators and other users.

Specifications:

• Onboard CPU: MOS Technology 6502 @ 2 MHz
• RAM: 8 kB
• ROM: 32 kB
• Disk controller: WD1770 or WD1772
• Communications controller: MOS Technology 8520A
• Transfer protocols: Standard and fast serial; burst mode; and commands for parallel interface (the latter not used)
• Disk type: 3.5″ inch
• Storage format: MFM, double density, double-sided
• Interface: CBM’s proprietary serial IEEE-488
• Power: 5 V @ 1 A (5 VA) – 12 V @ 0.5 A (6 VA)

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