Дисководы Commodore 8050, 8250 и SFD 1001: Технические характеристики и особенности.

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. They are notable for the disk drive having twice the processing power than the connected computer in having two 1MHz 6502 processors sharing operation of communication and disk operation, though only supporting 4k of main memory. The disk operating system is actually contained within the disk drive unit with commands being sent via the 8 bit GPIB interface where the system decodes the message and carries out the requested operation such as formatting a disk without further involvement from the connected computer.

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 8250 and SFD 1001 are double sided drives. Double 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 bottom side of disks formatted by double sided drives. 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).