VECHO / V8Power relies on video rows count BIOS variable being initialized, but it is not guaranteed to be initialized

[skiselev]

I've received the a pull request for my 8088 BIOS: skiselev/8088_bios#42

This pull request supposed to fix an issue where the 8088 BIOS does not initialize video row count BIOS variable at 0040:0084.

Upon closer investigation, it appears that the system BIOS is not guaranteed and not supposed to initialize this variable. VGA and EGA BIOS extensions do initialize it though.

The code here

V8Power/SOURCE/COMMON.INC

Line 2127 in 7852abe

mov bl, [es:0x0084]

should be updated to validate that the BIOS indeed populates the right value in that variable, or use some another way to detect the screen height