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Within DOS there are several variations to use 8" floppy disk drives:

Pure DOS
V1 + Software
V1 + Hardware
V3 + Software
Pure Disk Imaging

I have written a lot about operating 8" floppy disk drives within the DOS (Microsoft or IBM compatible) operating system. This page is a basic introduction to the subject.

General

Back than, 8" floppy disk drives were never ever used in IBM compatible computers like the IBM PC or XT under the MS-DOS or PC-DOS operating system! The very first IBM-PC was introduced on August 12, 1981 [1]. This was the IBM PC 5150 (16-64K, one single-sided 5.25" floppy disk drive, 160 KByte).

Some basic facts:

Note: The parameters for the DOS 5.25" drive(s) are of course by no means complete. I have only mentioned the very first DOS disk format (single-sided, 160 KB); media descriptor FEh.

If you take a look at the source code of the first IBM ROM BIOS (Aug 1981), you can learn a lot just by reading it. As a reminder. At the beginning there was only one disk size of 160 KByte (1 x 40 x 8 x 512 / 1,024 = 160). Interrupt 13 (INT13) and the DISK BASE PARAMETERS are decisive for the DOS floppy operations.

Have a look at the following lines of the source code listing:

0041: DISK_POINTER variable
2303: DISKETTE_IO (INT13)
2317: → CALL GET_PARM
2676: GET_PARM
2681: → LDS,SI DISK_POINTER
2995: DISK_BASE ← DISK_POINTER
2999: → 2 (512 bytes/sector)
3000: → 8 (last sector of track)

As you can see, 512 bytes/sector and 8 sectors/track were fixed back then! Some parameters later changed in the direction to larger capacities, but never the number of bytes per sector. This has always remained the same at 512. Period!

The only reason why you can use an 8" drive alternatively under MS/PC-DOS is because it has the same physical parameters as a (later) 1.2 MB high density drive. You may say, yes, but there is the DRIVPARM command in CONFIG.SYS. Forget it, it doesn't work, believe me!

A very interesting article, which also deals with the history of 8" drives can be found in this thread (see post #7) from the Vintage Computing Federation. And here we go. You can use ...

Variation 1: Pure DOS

You can run a 8" floppy disk drive within DOS if your computer system (BIOS, floppy disk controller) supports a 1.2 MByte (HD) 5,25" floppy disk. You need a ...

good working 8" floppy disk drive, a
power supply and a
34p to 50p adapter.

This trick is possible because 8" drives have the same physical parameters as 5.25" (1.2 MByte) high density (HD) drives! Except for one thing: 77 tracks, not 80. In the early days 1.2 MByte drives were used as a direct replacement for the large and bulky 8" drives. Expample(s): Mitsubishi M4854-342M or TEAC FD-55G/GV/GR.

Here DOS is faked with a 1.2 MByte floppy drive with 80 tracks. But, 8" drives can only handle 77 tracks! If you use more than 77 tracks, the 8" drive will have a problem. Not dramatic but not nice. Who writes his disks down to the last three tracks? You can DOS format a DSDD 8" floppy simply with: „FORMAT A:“. But you will hear that the stepper cannot reach the last three tracks.

Access the both 8" standard logical DOS formats (250 KByte: 77 tracks, 26 sectors/track, 128 bytes/sector and 1.2 MByte: 77 tracks, 8 sectors/track, 1,024 bytes/sector) is not possible, not even with DRIVPARM or DRIVER.SYS!

Variation 2: Variation 1 + Software

If you want to have real file access to old 8" floppy disks you need additional software.

22DISK

CP/M-to-DOS Diskette Interchange Utility

22DISK is a product which enables one to convert files on diskette from various CP/M formats to MS-DOS, and vice versa.

Sydex.com Download link

FDFORMAT

DOS Formatting Utility

Try FDFORMAT A: /T:77. Afterwards you can make the floppy bootable with: SYS A:. The floppy boots without any problems. Even the media despriptor is set correctly to F9h.

FDFORMAT

8FORMAT

DOS Formatting Utility

8FORMAT is a multi-purpose DOS application that interfaces the floppy disk controller directly.

8FORMAT

Variation 3: Variation 1 + Hardware

If you want to have real file access to the first 8" standard logical DOS format (250 KByte: 77 tracks, 26 sectors/track, 128 bytes/sector) you need ...

CompatiCard I or IV

Floppy Disk Controller

The CompatiCard is a versatile floppy disk controller card for the IBM /PC, XT, AT and compatibles. The CompatiCard will support any combination of 5 inch (48 TPI, 96 TPI, or high capacity AT), 8 inch, and 3.5 inch drives. It will also support both single and double density on all drives for maximum flexibility.

CompatiCard

The CC IV has its own extended BIOS. The CC I has an old school NEC uPD765A (or Intel 8272A) with TTL design and external data separator.

Variation 4: Variation 3 + Software

If you want to have real file access to both 8" standard logical DOS format (250 KByte: 77 tracks, 26 sectors/track, 128 bytes/sector and 1.2 MByte: 77 tracks, 8 sectors/track, 1,024 bytes/sector) you need ...

CompatiCard & UniForm & UniDOS

Solve the Compatibility Crisis

UniForm-PC effectively transforms one of your existing IBM PC floppy disk drives to your choice of CP/M computer format, allowing you to read, write and format data diskettes for most popular micros, as well as copy files (using your DOS COPY command) to PC-DOS format.

Micro Solutions

Variation 5: Pure Disk Imaging

For pure disk imaging of 8" floppy disks you need ...

DOS: ImageDisk & a MFM & FM compatible floppy disk controller
Windows: A flux Hard- and Software like Kryoflux, Greaseweazle or FLUXTEEN

Information

IBM ROM BIOS (Aug 1981)

References

(↑) https://web.archive.org/web/20060814072723/http://www-03.ibm.com/ibm/history/exhibits/pc25/pc25_press.html