OSBYTE CALLS AND THE FOURMEG AND TWO MEGAHERTZ BOARDS

OSBYTE with A=&72 (114) - called by *SHADOW
X determines the action followed
X=0  all MODE changes produce SHADOW RAM handling
X=1  all MODE changes between 0 to 7 remove SHADOW RAM;
     all MODE changes between 128 and 135 produce SHADOW RAM
X=FF all MODE changes remove SHADOW RAM

OSBYTE with A=&73 (115)
X determines the SHADOW RAM bank used:
X= 0  SHADOW 0 (SHADOW bank 8)
X= 1  SHADOW 1 (SHADOW bank 9)

OSBYTE with A=&74 (116) (bank F)
No entry requirement
X returns the ASCII value of "S", signifying that the STL
fourmeg or two megahertz board is in place, included for
firmware writers such as Computer Concepts, to use the STL
SHADOW RAM.