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| • | ROM's marked '5000026' and '5000027'. Photos at here. |
| • | Note that the 5000027 ROM, which sits in socket U19, contains only part of cassette BASIC, and is reused in the later 11/08/82 revision of BIOS. Refer to 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 two people with a set of 08/16/82 BIOS ROM's (set = 5000026 and 5000027). |
| • | 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 an IBM 5150 (IBM PC). Refer to here. This would cause some diagnostic software (those that use model bytes alone) to incorrectly deduce that they are running on an IBM 5150. |
| • | 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. |
