IBM 5150/5160  -  Boot Using a 720K Diskette

In an IBM 5150 or 5160 (or 5155), a 1.44M diskette drive connected to the IBM floppy controller card (IBM 5.25" Diskette Drive Adapter) will not work at 1.44M capacity (due to lack of High Density support on the card), but will work with 720K diskettes.

  Ability            Comment
Boot Yes IBM DOS 3.3 and IBM DOS 6.2 known to work
Read Yes  
Write Yes  
Format [see below]  

Formatting a 720K diskette requires a driver to be loaded. Click here for more information

If you have an IBM 5150, and that 5150 has the 16KB-64KB version of the 5150 motherboard, click here for details of a known issue.

On Your IBM 5150/5160

Connect a 1.44M diskette drive to the IBM floppy controller in your 5150/5160 as drive A:
For the cable, you can use a standard twisted floppy cable in reverse to how it is normally used. [photo here]
Make sure that you use the floppy type of twisted cable, not the hard drive type. [photo here]

The 5150/5160 can now boot/read/write a 720K diskette.

(Formatting a 720K diskette is a different story. Click here for more info.)

Creating a 720K Boot Diskette Using Your 'Modern' Computer

Requirement: Your 'modern' computer has an OS of Windows 7 or earlier (limation because of Winimage).
Requirement: Your 'modern' computer has a 1.44M diskette drive (internal or USB).

1. Download WinImage software from http://www.winimage.com and then install it.

2. Obtain a 720K diskette that you are prepared to overwrite. See here for the difference between 720K and 1.44M diskettes.
    A 1.44M diskette with its density hole suitably covered may work instead - not a legitimate action, but it should work for the purpose of what we are about to do in the following steps.

3. Place the diskette into the 1.44M drive.

4. Download file ibm_dos_33_on_720k.imz   (an image file of a 720K sized IBM DOS 3.3 boot diskette) to your hard drive.

5. In Windows Explorer, double-click on the downloaded ibm_dos_33_on_720k.imz file.
    As a result, WinImage should open, showing the contents of the image file.

6. On the WinImage menu bar, select DISK and in the menu shown, verify that the drive selected is your 1.44M one.


7. On the WinImage menu bar, select DISK and then FORMAT AND WRITE DISK. WinImage should start formatting/writing the diskette.

8. When WinImage has finished formatting/writing the diskette, close WinImage.

You now have a 720K sized IBM DOS 3.3 boot diskette for your IBM 5150/5160.