IBM 5160  -  BIOS Revisions

On the 5160 motherboard, there are two BIOS ROM chips, one in socket U18 and the other in socket U19.

There were 4 revisions of the BIOS, differentiated by date (there are no version numbers).
The table below lists the dates, and the unique 7-digit IBM part numbers that are located on the top of the ROM chips.

Because of the apparent scarcity of the 5000026 chip, and other reasons, it is possible that the 08/16/82 revision was not publically released.  See here.

The date format used is MM/DD/YY.

  Part numbers, where BIOS supplied
in masked ROM form
Part numbers, where BIOS supplied
in EPROM form
ROM / EPROM type supplied Floppy/diskette
drive support
08/16/82 U18=5000026, U19=5000027   (photo)    U18=MK38000, U19=MK37000 360K See here
11/08/82 U18=1501512, U19=5000027   (photo)
U18=1501512, U19=6359116
   Varies - see photo 360K See notes 1 and 2 below
01/10/86 U18=62X0851, U19=62X0854 U18=62X0852, U19=62X0853   (photo)  Both 27256 360K, 1.2M, 720K See note 3 below
05/09/86 U18=62X0890, U19=68X4370   (photo) U18=59X7268, U19=62X0819   (photo)  Both 27256 360K, 1.2M, 720K See notes 3 and 4 below

Click here to see the memory layout of the BIOS chips within the IBM 5160.

More information is shown here at the Vintage Computer Forums.

BIOS replacement/upgrade

If your IBM 5160 motherboard does not have the 05/09/86 revision of BIOS, upgrading to the 05/09/86 revision is valid (although read note 4 below).

Unlike with modern computers, you can not simply 'flash' a new BIOS onto the 5160 motherboard - you need to physically replace the two BIOS ROM chips.  New BIOS ROM chips are normally created by 'burning' an image of the BIOS into suitable EPROM chips (via an EPROM programmer):

27256 EPROMs can be replaced with 27C256.

On the early IBM 5160 motherboards, the TMM23256/MK37000/MK38000 ROMs can in most cases be replaced with 27C256 EPROMs, but some brands of 27C256 may be unsuitable - see here

Click here for content images.

For the IBM 5160, use EPROMs that are rated at 250 ns, or less.  (Reference.)

Click here to see some people/companies that can supply and 'burn' EPROMs for you.

Hard drive support

In an IBM 5160, the motherboard BIOS does not influence the types/capacities of hard disk drives that can be used.  That is determined by the particular XT-class hard disk controller card that is fitted (and the operating system).

Note 1 In the 11/08/82 BIOS revision, 720K diskette operation is partially supported.  More information is here.
Note 2 Refer to the diagram here.
In the 11/08/82 BIOS revision, chip U19 contains part of cassette BASIC and thus is not critical to operation of the computer (only cassette BASIC is lost).
For that reason, if the POST discovers that U19 has failed, the POST will display "F6000 ROM" and allow booting to continue.

This is not the case for the later BIOS revisions, because in those, U19 also contains part of the BIOS. If U19 fails in those, the motherboard will appear 'dead'.
Note 3 A 1.2M floppy drive is a high density (HD) drive. The floppy controller that IBM supplied in the IBM 5160 (photo) does not support HD operation.
Note 4 See here for details of a possible problem caused by the 05/09/86 BIOS.