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IBM 5150/5155/5160  -  Boot Using a 720K Diskette


In an IBM 5150 or 5155 or 5160, a 1.44M diskette drive connected to the IBM 5.25" Diskette Drive Adapter will not work at 1.44M capacity (in part, 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]  

Click here for information about formatting a 720K diskette.

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 5150/5155/5160

Connect a 'standard' 1.44M diskette drive to the 'IBM 5.25" Diskette Drive Adapter' in your 5150/5155/5160 as drive A:  (physical drive 0)
Some connection options:
- To use the existing IBM supplied cable, one of these plugged into the 1.44M diskette drive.  A source of those is at here.
- You can use the cable pictured at here in reverse to how it is normally used.  Make sure that you use the floppy type of twisted cable, not the hard drive type. [photo here]

The 5150/5155/5160 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 a 1.44M diskette drive, internal or USB.
Requirement: If using a USB type of 1.44M diskette drive, that the drive also supports 720K diskettes. See here.

The following instructions are for WinImage version 11.00, running in Windows 11.

Note that following, we will not be getting WinImage 11.00 software to do any formatting of the 720K diskette.  Instead, formatting will be done at a command prompt prior to using WinImage.  That will verify that Windows 11 is 'happy' about writing to a 720K diskette; something that I think is good to do before running WinImage.

Step 1 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 should work instead - not a legitimate action, but it should work for the purpose of what we are about to do in the following steps.
Step 2 Place the 720K diskette into the 1.44M drive.
Step 3 Format the 720K diskette per here.  During the formatting procedure, verify that you see "Verifying 720 KB" and "713.0 KB total disk space" in the displayed text.
Step 4 For later use in this procedure, download image file ibm_dos_33_on_720k.imz   (an image file of a 720K sized IBM DOS 3.3 boot diskette) to your hard drive.
Step 5 Download WinImage 11.00 software from http://www.winimage.com and then install it.
Step 6 Of the two WinImage icons/shortcuts, click on the 'WinImage (administrator)' one.  A 'User Account Control' window will open.  In that window, click on the 'Yes' button.  WinImage 11.00 will open.
Step 7 [WinImage]: On the menu bar, click on {Disk}, and in the menu shown, verify that the drive selected is your 1.44M one.

winimage_drive_select.png
Step 8 [WinImage]: On the menu bar, click on {File} then {Open}.  Navigate to where you downloaded the image file of ibm_dos_33_on_720k.imz to, and then select that file.  WinImage will open the file, then display the 11 files within, like this.

NOTE:  Not shown to you are non-file things in ibm_dos_33_on_720k.imz, such as the MBR and FAT's.
Step 9 [WinImage]: On the menu bar, click on {Image} then {Image Information}.  In the window that opens, verify that the 'Total Image Space' figure is 737,280 (i.e. 720 KB).  Close the window.
Step 10 [WinImage]: On the menu bar, click on {Disk} then {Write Disk}.  You will hear the diskette being accessed, and then you will see a window containing "Disk A: is not empty ........ Do you want to continue?".  Click on the {Yes} button.  A 'Writing disk' window will appear, showing you the progress of the image being written to the diskette.

NOTE:  We are using {Write Disk} instead of {Format and write disk}, because the diskette has already been formatted at step 3.
Step 11 [WinImage]: When writing is complete, close WinImage.


You now have a 720K sized IBM DOS 3.3 boot diskette for your IBM 5150/5155/5160.