Table 2 -- BIOS RAM data areas for RTC functions
        
        0040:006C   4 bytes   System Timer Tick Counter*
        0040:0070   1 byte    24 hour rollover flag*
        0040:0098   4 bytes   Far pointer to user wait flag
        0040:009C   4 bytes   Wait count
        0040:00A0   1 byte    Wait active flag
                              Bit 7     = 1  Wait time elapsed
                              Bits 6-1  = Reserved
                              Bit 0     = 1  Wait active
        
        * The System Timer Tick Counter and 24 hour rollover flag are 
          used by the System Timer ISR (INT 8) on the PC/XT as well as 
          AT.