On 5/30/2025 4:58 AM, Bernd Böckmann via Freedos-devel wrote:
I finally got my hands on a machine that shows the symptom of BDA 40:96 getting
changed, and I was able to identify the problem.
When the PC starts, BDA 40:96 is initially zero. As soon as the users enters
some specific keys (like the arrow keys), the value at 40:96 changes to 0x10.
So the BIOS seems to do some keyboard auto detection.
Sorry to intrude on this technical discussion, but an open source PM
debugger such as 386SWAT can trivially be set to detect reads and/or
writes to any location such as 40:96. Set it to detect writes, and it
pops up exactly when they happen.
It can be loaded from CONFIG.SYS. Perhaps the events you want to trap
appear before CONFIG.SYS is processed, in which case this tool won't
help. Otherwise, it can be very helpful.
I realize that you might not consider 386SWAT to be an acceptable
addition to FreeDOS, but that doesn't mean you can't use it solely for
debugging situations such as this.
--
_______________________________________________________________
Bob Smith - bsm...@sudleyplace.com
http://www.sudleyplace.com - http://www.nars2000.org
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