Parent 

IBM 5160  -  Unknown Status of 08/16/82 BIOS Revision for Motherboard


ROMS marked '5000026' and '5000027'.  Photos at here.
   
The 'Upgrading and Repairing PCs' book (Scott Mueller), and most other information sources, do not include this BIOS in their list of BIOS' for the IBM 5160.
   
To date, I am only aware of one person with a set of 08/16/82 BIOS ROMs.
   
The IBM 5160 was announced on March 1983.
The date of both the 08/16/82 BIOS and 11/08/82 BIOS precede that date, with the latter being some 7 months prior to March 1983.
So at least 7 months before 5160 announcement, IBM found reason to produce another revision of BIOS.
   
An observation is that the model byte (A.K.A. model code, ID byte) in the 08/16/82 BIOS is FF, reflecting a 5150 (PC).  Refer to here.
   
Following are some possibilities that I can think of:

POSSIBLILITY #1

• The 08/16/82 BIOS was not released to the public.
• Some 08/16/82 BIOS equipped 5160's that IBM held on to internally, eventually made it into the public domain.

POSSIBLILITY #2

• Although the 08/16/82 BIOS was replaced by the 11/08/82 BIOS at least 7 months prior to 5160 announcement, IBM did not consider the 08/16/82 BIOS to be 'unreleasable', and consequently, already-manufactured stocks of 08/16/82 BIOS ROM chips went out in some early batches of the 5160.