Commodore 8050
Encyclopedia
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/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 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.
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 2031LP
), often used by bulletin board system
s for their physical similarity to 1541s and high capacity and speed.
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
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
drives for Commodore International
Commodore International
Commodore is the commonly used name for Commodore Business Machines , the U.S.-based home computer manufacturer and electronics manufacturer headquartered in West Chester, Pennsylvania, which also housed Commodore's corporate parent company, Commodore International Limited...
computers. They used a wide rectangular steel case form similar to that of the Commodore 4040
Commodore 4040
The Commodore 4040 and its sibling, the 2040 and the European marketed 3040, were dual unit 5¼" floppy disk drives for Commodore International computers...
, and used the IEEE-488
IEEE-488
IEEE-488 is a short-range digital communications bus specification. It was created for use with automated test equipment in the late 1960s, and is still in use for that purpose. IEEE-488 was created as HP-IB , and is commonly called GPIB...
interface common to Commodore PET/CBM
Commodore PET
The Commodore PET was a home/personal computer produced from 1977 by Commodore International...
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
Double density
Double density, often shortened DD, is a capacity designation on magnetic storage, usually floppy disks. It describes the use of an encoding of information, which can encode on average twice as many bits per time unit compared to single 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
Commodore 1541
The Commodore 1541 , made by Commodore International, was the best-known floppy disk drive for the Commodore 64 home computer. The 1541 was a single-sided 170 kilobyte drive for 5¼" disks...
or Commodore 4040
Commodore 4040
The Commodore 4040 and its sibling, the 2040 and the European marketed 3040, were dual unit 5¼" floppy disk drives for Commodore International computers...
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
Commodore 1541
The Commodore 1541 , made by Commodore International, was the best-known floppy disk drive for the Commodore 64 home computer. The 1541 was a single-sided 170 kilobyte drive for 5¼" disks...
style case (similarly to the Commodore 2031LP
Commodore 2031
The Commodore 2031 and Commodore 4031 were single unit 5¼" floppy disk drives for Commodore International computers. They used a similar steel case form to the Commodore 9060/9090 hard disk drives, and used the IEEE-488 interface common to Commodore PET/CBM computers...
), often used by bulletin board system
Bulletin board system
A Bulletin Board System, or BBS, is a computer system running software that allows users to connect and log in to the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and data, reading news and bulletins, and exchanging...
s 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