IBM 5150 - BIOS upgrade on 16K-64K motherboard - SW2 example


When upgrading the BIOS on a 16K-64K motherboard to the 10/27/82 one, the setting of SW2-5 needs to be changed in most cases.
The following is an example - 128 KB of RAM.

BIOS
SW2-1
SW2-2
SW2-3
SW2-4
SW2-5
SW2-6
SW2-7
SW2-8
    Comment
04/24/81
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
 See note 1
10/19/81
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
 See note 1
10/27/82
ON
OFF
ON
ON
ON
OFF
OFF
OFF
 




Note 1:
For the 04/24/81 and 10/19/81 BIOS, IBM instructed that switches 5 to 8 on SW2 be set to off (even though it is a 'do not care' situation).
You can see that instruction on the bottom of page 2-28 in the AUG81 edition of the Technical Reference manual.