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IBM 5150/5160 - Adding DRIVER.SYS for Full 720K Diskette Support


Background

The 5150 BIOS and the first revision of the 5160 BIOS (11/08/82) have no built-in support for 720K diskettes.

However, in machines fitted with those BIOS', if you replace the 360K floppy drive with a 1.44M drive, you will discover that the 5150/5160 will boot/read/write 720K diskettes.
The one operation that fails is the format of a 720K diskette. Either the diskette formats as 360K, or error messages such as "Parameters not supported" or "Invalid parameter" are seen.

In such cases, the following procedure (one of a few) will enable a 720K diskette to be formatted (as 720K).

Of course, an option is to format the diskettes via Windows on your modern computer. Click here for details.


Procedure if 1.44M drive is A:

Assuming that on your 5150/5160, the file DRIVER.SYS is located in the C:\DOS directory, then add the following line to CONFIG.SYS:

DEVICE=C:\DOS\DRIVER.SYS /D:0 /F:2

Reboot your 5150/5160.
You will probably see a line displayed that looks a lot like, "Loaded External Disk Driver for Drive D".

What you will now find is that the 720K drive is accessible as either A: or D:
Drive A: is the direct route.
Drive D: is via the DRIVER.SYS driver ( configured for 720K operation because of the /F:2 )

If you now do a format of D: (simply "FORMAT D:" is enough), the 720K diskette will format as 720K.


Procedure if 1.44M drive is B:

Assuming that on your 5150/5160, the file DRIVER.SYS is located in the C:\DOS directory, then add the following line to CONFIG.SYS:

DEVICE=C:\DOS\DRIVER.SYS /D:1 /F:2

Reboot your 5150/5160.
You will probably see a line displayed that looks a lot like, "Loaded External Disk Driver for Drive D".

What you will now find is that the 720K drive is accessible as either B: or D:
Drive B: is the direct route.
Drive D: is via the DRIVER.SYS driver ( configured for 720K operation because of the /F:2 )

If you now do a format of D: (simply "FORMAT D:" is enough), the 720K diskette will format as 720K.