AH = 88h on return: CF = 80h for PC, PCjr = 86h for XT and Model 30 = other machines, set for error, clear for success AX = number of contiguous 1k blocks of memory starting at address 1024k (100000h) - works only on 80286 and 80386 machines - retrieves bytes 30 and 31 from the CMOS RAM (this data is set by the boot memory scan