FDD – Diskettes

Contents

• Introduction
• Sizes
• Hard or Soft
• Index Hole
• Write Protect/Enable Notch
• Examples
• Product List
• Documents
• Links

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Introduction

What is a diskette?

Source: 3M Diskette Ref. Man.

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Sizes

Basically there are four different types or sizes of floppy disks / diskettes:

Diskettes

1. 8 inch floppy disk

• a.k.a -> FLOPPY DISK
• 203 mm (8") x 203 mm

5.25 inch floppy disk

• a.k.a -> MINI DISKETTE, MINI DISK, MINI FLOPPY
• 133 mm (5.25") x 133 mm

3.5 inch floppy disk

• a.k.a -> MICRO DISKETTE, MICRO DISK, MICRO FLOPPY
• 90 mm (3.5") x 93 mm

3 inch floppy disk

• a.k.a -> COMPACT FLOPPY DISK
• 80 mm (3") x 100 mm

The original name FLOPPY DISK was later simply adopted with the advent of the IBM PC and XT.

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Hard or Soft

In addition to size, there is also a distinction between soft- and hard-sectored disks. The 3.5" and 3" floppy disks are all soft-sectored. Hard-sectored floppy disks were never used in IBM-compatible computers.

Here you can see an example of a 8 inch floppy disks with 32 sector holes.

Diskette Types / 8 inch & 5,25 inch
Source: 3M Diskette Ref. Man.

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Index Hole

Below are a few illustrations showing the different index holes using the example of 3M floppy disks.

Index hole / 5,25 inch
Source: 3M Diskette Ref. Man.

Index hole / 8 inch / single sided
Source: 3M Diskette Ref. Man.

Index hole / 8 inch / double sided
Source: 3M Diskette Ref. Man.

Index hole / 8 inch / flippy disks
Source: 3M Diskette Ref. Man.

This type (SS-DD-R-128/F) was used in DEC systems, for example.

Index hole / 8 inch / hard sectored
Source: 3M Diskette Ref. Man.

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Write Protect/Enable Notch

8 inch

... floppy disks can only be written to when the write protect notch is COVERED.

5.25 inch

... floppy disks can only be written to when the write ENABLE notch is UNCOVERED.

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Examples

Hard-sectored

Because hard-sectored 5.25 inch floppy disks are very difficult to find/buy today, Mike Douglas invented/constructed the so-called Virtual Sector Generator (VSG).

5.25 inch / 10 Sector Holes

Floppy disks with 16 sector holes are not often found, but those with 10 holes are extremely rare. These disks were used in the following computer systems:

• Heathkit H89
• North Star Horizon

Scotch 3M / 744-10 / 84-9801-3937-6 / single sided

Scotch 3M / 745-10 RH / 84-9801-4421-0 / double sided

Scotch 3M / 745-10 RH / 84-9801-4421-0 / double sided

I was able to buy a pack (745-10 RH, 10 pieces, NOS) on ebay US on 01.09.2021.

Update: Today (13.09.2021) I hold a hard-sectored 5.25" inch floppy disk (double sided, 10 sector holes) in my hands for the first time. A piece of history.

5.25 inch / 16 Sector Holes

These disks were used in the following computer systems:

• AES Data Inc.: 7100 Office System
• Honeywell Bull: Questar/M
• Vector Graphic: Vector 3

Scotch 3M / 744D-16 RH / 84-9801-4748-6

Scotch 3M / 744D-16 RH / 84-9801-4748-6

8 inch / 32 Sector Holes

See here: 8 inch floppy disks.

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Delivery Programme / Product List

3M

8 inch

3M / delivery programme / 8 inch

5.25 inch

3M / delivery programme / 5.25 inch

boeder

8 inch

boeder / delivery programme / 8 inch

boeder / delivery programme / 8 inch

5.25 inch

boeder / delivery programme / 5.25 inch

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Documents & Information

• 3M Diskette Reference Manual (May 1983)
• The IBM Diskette General Information Manual (Jul 1980)
• boeder Delivery Programme 8 inch (TXT)

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External Links

• Wikipedia: History of the floppy disk
• Herb Johnson: Tech information on floppy disks drives and media. This article is very long, but you will probably find everything on this subject here!
• Herb Johnson / Chuck Guzis: Use of HD and DD drives, diskettes