Commodore 8250

Commodore 8050

Commodore 8050 floppy-disk drive, with CBM 2001 PC
Manufacturer	Commodore Business Machines, Inc.
Type	Floppy drive
Release date	1980 (1980)
Introductory price	USD 1695 (1980) USD 4,900 (2017 equivalent)
Media	2x 5¼" double-sided, double-density
Operating system	CBM DOS 2.5/2.7
CPU	2x MOS 6502 @ 1 MHz
Memory	4 kB RAM 16 kB ROM
Storage	521 kB/side, 1042 kB/disk
Connectivity	Parallel IEEE-488
Power	110-117V, 220-240V, 50W
Dimensions	6.5 in × 15.0 in × 14.35 in (165 mm × 381 mm × 364 mm)
Weight	28 lb (13 kg)
Backward compatibility	PET, 4000-series, 8000-series, B128; Commodore 64, VIC-20 with IEEE-488 adapter

The Commodore 8050, Commodore 8250, and Commodore SFD-1001 are 5¼-inch floppy disk drives manufactured by Commodore International, primarily for its 8-bit CBM and PET series of computers. The drives offered improved storage capacities over previous Commodore drive models.

All three models utilize 5¼-inch double density floppy disks with a track spacing of 100 tracks-per-inch, for a total of 77 logical tracks per side. Data is encoded using Commodore's proprietary group coded recording scheme. Soft sectoring is used for track alignment. Like most other Commodore disk drives, these drives utilize zone bit recording to maintain an average bit density across the entire disk. Formatted capacity is approximately 0.5 megabyte per side, or 1 megabyte (1,066,496 bytes) in 4166 blocks total.

The 8050 is a single-sided drive, whereas the 8520 and SFD-1001 are dual-sided drives. Dual-sided drives can fully read and write to disks formatted by single-sided drives, but single-sided drives can only read and write to the front side of disks formatted by dual-sided drives.

Both the 8050 and 8520 are housed in a dual-drive case similar to the Commodore 4040 drive. The SFD-1001 is housed in a single-drive case similar to the Commodore 1541. The 8520lp, a low-profile revision of the 8520, is housed in a shorter dual-drive case that is stylistically similar to the SFD-1001. All models include an internal power supply and a IEEE-488 data connector on the rear of the case. The 8050 and 8520 include latch sensors that can detect when a disk is inserted or removed.

These drives are not dual-mode, so they cannot read or write 5¼-inch disks formatted by lower-capacity 48-tpi models, such as the Commodore 1541 or 4040. They also cannot read or write 5¼-inch disks formatted by 96-tpi drives, such as the 640 kilobyte IBM PC disk or 880 kilobyte Commodore Amiga disk, due to the minor difference in track spacing. Lastly, they cannot read or write high-density 5¼-inch disks due to both the difference in track spacing and the difference in write head coercivity (300-oersted for double-density, 600-oersted for high-density).