2M-XBIOS


This page describes the procedure for using 2M-XBIOS software and a 16-bit floppy controller, to get a 1.2M floppy drive operating as B: on an IBM 5150 (IBM PC) or IBM 5155 (IBM Portable PC) or IBM 5160 (IBM XT), at 1.2M capacity.

(For a 1.44M drive instead, see here.)


STEP 1:  Locate a 16-Bit Floppy Controller

Locate a 16-bit floppy controller card.  Below is pictured the card that I used.

The card needs to suport High Density (HD) operation.  Within the IBM Personal Computer family of computers, HD was introduced in IBM's first 16-bit personal computer, the IBM 5170 (IBM AT).  Because of that, it is a very safe bet that any 16-bit floppy controller you find will support HD operation.





STEP 2:  Install the 16-Bit Controller

Install the 16-bit controller into one of the computer's 8-bit slots.
Yes, the shorter of the controller's two edge connectors will be 'floating in space'.

If your computer is an IBM 5155 or IBM 5160, do not use slot 8.

You cannot use the 16-bit floppy controller in addition to the existing 8-bit floppy controller, because the two cards will conflict.  The 8-bit floppy controller needs to be removed.

Note that the controller I used also had IDE functionality.  I did not need to disable that IDE functionality (because the IDE functionality did not conflict with any other card in my PC).



STEP 3:  Connect Floppy Drives

Connect floppy drives to the controller, and of course, also connect the drives to the power supply.

I used a 360K drive for A: and a 1.2M drive for B:



STEP 4:  Preparation For 2M-XBIOS

From the following table, note the numbers that correspond to your drives.
These numbers are required for the 2M-XBIOS software.

Size	Number	Comment/s
360K	1	DD.
1.2M	2	HD.   1.2M requires DOS 3.0 or later.
720K	3	DD.   720K requires DOS 3.2 or later.
1.44M	4	HD.   1.44M requires DOS 3.3 or later.
2.88M	5	Requires a controller that supports ED (1 Mbits/s transfer rate).   2.88M requires DOS 5 or later.

So, for my configuration, I noted that drive A: (a 360K) is 1, and drive B: (a 1.2M) is 2.



STEP 5:  Install 2M-XBIOS Onto C:

5.1   Get the 2M-XBIOS.EXE file from here and then copy it to the root of the C: drive.

5.2   Add the following line to the CONFIG.SYS file on the C: drive, substituting the "1" and "2" for the numbers that you determined for your A: and B: drives at step 4.

         DEVICE=2M-XBIOS.EXE A:1 B:2 /13



STEP 6:  Reboot

Reboot the computer.
During the boot up sequence, you should see something like:

         2M-XBIOS 1.3 installed on A:360K B:1.2M [INT 13h]


When DOS then gives you the C:\> prompt, you should find that you can use the 1.2M drive (at 1.2M capacity).

Note that support for 1.2M drives was not introduced into DOS until version 3.0