testbios and the system timer

ron minnich rminnich at lanl.gov
Thu Jun 3 15:40:00 CEST 2004

On Thu, 3 Jun 2004, Richard Smith wrote:

> This will only skip the jump (and do the BX decrement) if ax is zero. 
> For ax to be zero the result of the 2's complement subtraction must be 
> zero or the when the 2 reads are the same number.  But I just don't see 
> how this would happen repeatably at .6us per ISA IO.

All I know is BIOS code sucks and it looks like VGA BIOS code is worse 
than BIOS code. IT's amazing that any of it ever worked at all.


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