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Commodore 8050 floppy-disk drive, with CBM 2001 PC

The Commodore 8050 and Commodore 8250 are dual-unit 5¼" floppy disk drives for Commodore International computers. They used a wide rectangular steel case form similar to that of the Commodore 4040, and used the IEEE-488 interface common to Commodore PET/CBM computers.

The 8050 was a single sided drive, whereas the 8250 could use both sides of a disk simultaneously. Both used a "quad" density format storing approximately 0.5 megabyte per side. The density of media was similar to later PC high density floppy disks, but the 8050 and 8250 could not use PC high density disks reliably. Since quad-density disks were rare even at the time, users quickly found that typical double-density floppy disks had enough magnetic media density to work in these drives.

These drives are not dual-mode, so they cannot read or write disks formatted by the more common lower-capacity Commodore 1541 or Commodore 4040 models.

Some variants of these drives exist. The Commodore 8250LP is the 8250 in a lower profile, tan-colored case. The Commodore SFD-1001 is a single-drive version of the 8250 in a Commodore 1541-style case (similarly to the Commodore 2031LP), often used by bulletin board systems for their physical similarity to 1541s and high capacity and speed.

Disk Layout

Track	Sectors Per Track (256 bytes)	Sectors
1-39, 78-116	29	1131
40-53, 117-130	27	378
54-64, 131-141	25	275
65-77, 142-154	23	299

Total Sectors: 2083 (4166 for the 8250)

The disk header is on 39/0 (track 39, sector 0), with the directory residing on the remaining 28 sectors of track 39.

Header Layout 39/0

$00–01 T/S reference to the first BAM (Block Allocation Map) sector
    02 DOS version ('C')
 06-16 Disk label, $A0 padded
 18-19 Disk ID
 1B-1C DOS type('2C')

The BAM (Block Allocation Map) begins on 38/0 (track 38, sector 0), and continues on 38/3. On the 8250, the BAM extends further to 38/6 and 38/9. The remaining sectors on track 38 are available for general use.

BAM Layout 38/0, 3, (6, 9)

$00–01 T/S reference to the next BAM sector, or 00/FF if last.
    02 DOS version ('C')
    04 Lowest BAM track in this block
    05 Highest+1 BAM track in this block
 06-FF BAM for 50 tracks

References

Commodore 8050 Brochure
[1] TOOLS specifically for the SFD1001 & 8250 Drives.
Commodore Knowledge Base
Technical comparison of Commodore floppy drives (with drive capacities)
Commodore Dual Disk Drives

This microcomputer- or microprocessor-related article is a stub. You can help Wikipedia by expanding it.

@@ Line 6: / Line 6: @@
 [[File:Commodore CBM 2001 & 8050.jpg|thumb|Commodore 8050 floppy-disk drive, with CBM 2001 PC]]
-The '''Commodore 8050''' and '''Commodore 8250''' were dual unit 5¼" [[floppy disk]] drives for [[Commodore International]] computers.  They used a wide rectangular steel case form similar to that of the [[Commodore 4040]], and used the [[IEEE-488]] interface common to [[Commodore PET|Commodore PET/CBM]] computers.
+The '''Commodore 8050''' and '''Commodore 8250''' are dual-unit 5¼" [[floppy disk]] drives for [[Commodore International]] computers.  They used a wide rectangular steel case form similar to that of the [[Commodore 4040]], and used the [[IEEE-488]] interface common to [[Commodore PET|Commodore PET/CBM]] computers.
-The '''8050''' was a single sided drive, whereas the '''8250''' could use both sides of a disk simultaneously.  Both used a "quad" density format storing approximately 0.5 megabyte per side.  The density of media was similar to later PC [[high density]] floppy disks, but the 8050 and 8250 could not use PC high density disks reliably.  Since "quad" density disks were rare even at the time, users quickly found that typical [[double density]] floppy disks had enough magnetic media density to work in these drives.
+The '''8050''' was a single sided drive, whereas the '''8250''' could use both sides of a disk simultaneously.  Both used a "quad" density format storing approximately 0.5 megabyte per side.  The density of media was similar to later PC [[high density]] floppy disks, but the 8050 and 8250 could not use PC high density disks reliably.  Since quad-density disks were rare even at the time, users quickly found that typical [[double-density]] floppy disks had enough magnetic media density to work in these drives.
-These drives were not '''dual mode''', so they could not read or write disks formatted by the more common lower capacity [[Commodore 1541]] or [[Commodore 4040]] models.
+These drives are not '''dual-mode''', so they cannot read or write disks formatted by the more common lower-capacity [[Commodore 1541]] or [[Commodore 4040]] models.
-Some variants of these drives existed.  The '''Commodore 8250LP''' was the '''8250''' in a lower profile, tan-colored case.  The '''Commodore SFD-1001''' was a single drive version of the '''8250''' in a [[Commodore 1541]] style case (similarly to the [[Commodore 2031|Commodore 2031LP]]), often used by [[bulletin board system]]s for their physical similarity to '''1541'''s and high capacity and speed.
+Some variants of these drives exist.  The '''Commodore 8250LP''' is the '''8250''' in a lower profile, tan-colored case.  The '''Commodore SFD-1001''' is a single-drive version of the '''8250''' in a [[Commodore 1541]]-style case (similarly to the [[Commodore 2031|Commodore 2031LP]]), often used by [[bulletin board system]]s for their physical similarity to '''1541'''s and high capacity and speed.
 ==Disk Layout==