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IBM 5150  -  BIOS Revisions


There were 3 revisions of the BIOS, differentiated by date (there are no version numbers).
The date format used is MM/DD/YY.

On the 5150 motherboard, the ROM in socket U33 contains the BIOS.
Note that the ROMs in sockets U29/U30/U31/U32 are not part of the BIOS.  Those ROMs contain cassette BASIC.

The photos below are merely representative.

If required, see here for information on substitution.


5150_u33_5700051.jpg Dated  04/24/81

Has the IBM part number of "5700051" printed on it.

Useable only on motherboards of type 16KB-64KB

Limitation 1: By design, only recognises up to 544 KB of RAM.
Limitation 2: The BIOS expansion ROM in cards that have one is not recognised. Examples: EGA/VGA cards, hard disk controllers.

(photo source: Framer at the VCF)
   
5150_u33_5700671.jpg Dated  10/19/81

Has the IBM part number of "5700671" printed on it.

Useable only on motherboards of type 16KB-64KB

Has the same two limitations as the earlier BIOS.
   
5150_u33_1501476.jpg Dated  10/27/82

Has the IBM part number of "1501476" printed on it.

Useable on motherboards of types 16KB-64KB and 64KB-256KB

The two limitations of the earlier BIOS' are removed.

Due to bugs, this BIOS requires that all 4 banks of motherboard RAM be populated.