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IBM 5150  -  Floppy Drive Support


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Cable and Termination

• A diagram is at here.

• You need to use the particular cable shown at here.  The IBM controller expects it.  The cable manipulates both the motor-on and drive-select lines.

• Do not accidentally use the hard drive type of twisted cable.  Difference shown at here.

• For 5.25" drives, terminate as appropriate, per the diagram at here.


5.25" 180K drives

These are found in very early 5150's.

In effect, this is a single-sided version of the 360K drive.  See here for a way to tell the difference.  For single-sided double-density floppies.

Initially, they were referred to by IBM as "160 KB Diskette Drive", 160 KB because IBM DOS 1.x uses 8 sectors per track.  DOS 2.0 introduced support for 9 sectors per track, which increased the floppy capacity to 180 KB.


DOS:  DOS 1.0 or later for 160 KB floppies.
DOS 2.0 or later for 180 KB floppies.
BIOS:  The IBM BIOS (all three revisions) on the IBM 5150 motherboard has full support for 180K drives/floppies.
Hardware:  The floppy controller (photo) that IBM supplied in the IBM 5150 supports 180K drives.


5.25" 360K drives

Initially, this was referred to by IBM as a "320 KB Diskette Drive", 320 KB because IBM DOS 1.1 uses 8 sectors per track.  DOS 2.0 introduced support for 9 sectors per track, which increased the floppy capacity to 360 KB.  Subsequently, it was commonly referred to as a '360K' drive.


DOS:  DOS 1.1 or later for 320 KB floppies.
DOS 2.0 or later for 360 KB floppies.

NOTE:  DOS 1.0 does not know about double-sided floppy drives. It will treat the drive as single-sided.
BIOS:  The IBM BIOS (all three revisions) on the IBM 5150 motherboard has full support for 360K drives/floppies.
Hardware:  The floppy controller (photo) that IBM supplied in the IBM 5150 supports 360K drives.


5.25" 1.2M drives

DOS:  DOS 3.0 or later  (3.0 introduced DOS support for 1.2M floppies).
BIOS:  The IBM BIOS (all three revisions) on the IBM 5150 motherboard does not support 1.2M drives/diskettes.
Hardware:  The floppy controller (photo) that IBM supplied in the IBM 5150 does not support 1.2M drives.


To gain 1.2M operation, one possible solution is here.  Another possible solution is here.


3.5" 720K drives

720K drives are uncommon.

DOS:  DOS 3.2 or later  (3.2 introduced DOS support for 720K diskettes).
BIOS:  The IBM BIOS (all three revisions) on the IBM 5150 motherboard has partial support 720K drives/diskettes.
See note 1 below.
Hardware:  The floppy controller (photo) that IBM supplied in the IBM 5150 supports 720K drives.


Note 1 You can read from and write to 720K diskettes, but not format.
Use of one of the options shown at here will give you the ability to format.


3.5" 1.44M drives

DOS:  DOS 3.3 or later  (3.3 introduced DOS support for 1.44M diskettes).
BIOS:  The IBM BIOS (all three revisions) on the IBM 5150 motherboard does not support 1.44M drives/diskettes.
Hardware:  The floppy controller (photo) that IBM supplied in the IBM 5150 does not support 1.44M drives.


720K diskette in 1.44M drive

If a 1.44M drive is connected to the IBM supplied controller, it will be discovered that 720K diskettes can be used.
You can read from and write to 720K diskettes, but not format.
Use of one of the options shown at here will give you the ability to format.

Note that the 1.44M drive can be attached to either the controller's internal connector (P2) or external connector (J1).  For internal connection, see here.  For external connection, see here.


1.44M diskette in 1.44M drive

One possible solution is here.
Another possible solution is here.
Another possible solution is here.