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[ The PC Guide | Systems and Components Reference Guide | Floppy Disk Drives | Floppy Disk Formats and Logical Structures ]

Summary of Floppy Disk Types and Specifications

The following table shows a summary of the various floppy disk specifications provided in other sections of this chapter, for each of the five major floppy disk types:

Category

Specification

360 KB 5.25"

1.2 MB 5.25"

720 KB 3.5"

1.44 MB 3.5"

2.88 MB 3.5"

Drive

Read/Write Heads (Data Surfaces)

2

2

2

2

2

Spindle Motor Speed

300 RPM

360 RPM

300 RPM

300 RPM

300 RPM

Controller

Minimum Controller Transfer Rate

250 Kbits/s

500 Kbits/s

250 Kbits/s

500 Kbits/s

1 Mbits/s

Media

Track Density (TPI)

48

96

135

135

135

Bit Density (BPI)

5,876

9,869

8,717

17,434

34,868

Density Name

Double Density (DD)

High Density (HD)

Double Density (DD)

High Density (HD)

Extra-High Density (ED)

Geometry

Tracks (Cylinders)

40

80

80

80

80

Sectors Per Track/Cylinder

9

15

9

18

36

Total Sectors Per Disk

720

2,400

1,440

2,880

5,760

File System

Cluster Size

2 sectors

1 sector

2 sectors

1 sector

2 sectors

Maximum Root Directory Entries

112

224

112

224

448

Capacity

Unformatted Capacity

~480 KB

~ 1.6 MB

~1 MB

~2 MB

~4 MB

Formatted Capacity (binary kilobytes)

360

1,200

720

1,440

2,880

Formatted Capacity (bytes)

368,640

1,228,800

737,280

1,474,560

2,949,120

File System Overhead (bytes)

6,144

14,848

7,168

16,896

17,408

Total Usable Capacity (bytes)

362,496

1,213,952

730,112

1,457,664

2,931,712

Total Usable Capacity (binary KB)

354

1,185.5

713

1,423.5

2,863

Total Usable Capacity (binary MB)

0.346

1.158

0.696

1.390

2.796

Next: Floppy Disk Interfacing and Configuration


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