Figure 1--CMOS RAM Data Descriptions Real time clock data Offset Size Description 00 1 Byte Current second in BCD 01 1 Byte Alarm second in BCD 02 1 Byte Current minute in BCD 03 1 Byte Alarm minute in BCD 04 1 Byte Current hour in BCD 05 1 Byte Alarm hour in BCD 06 1 Byte Current day of week in BCD 07 1 Byte Current day in BCD 08 1 Byte Current month in BCD 09 1 Byte Current year in BCD Status registers (See Figure 1) Offset Size Description 0A 1 Byte Status Register A 0B 1 Byte Status Register B 0C 1 Byte Status Register C 0D 1 Byte Status Register D Configuration data Offset Size Description 0E 1 Byte Diagnostic Status Bit 1 = 1 Real time clock lost power Bit 6 = 1 CMOS checksum is bad Bit 5 = 1 invalid configuration informa- tion found at POST Bit 4 = 1 Memory size compare error at POST Bit 3 = 1 Fixed disk or adapter failed initialization Bit 2 = 1 CMOS time invalid Bits 1-0 = Reserved 0F 1 byte Reason for shutdown 00 = Power on or reset 01 = Memory size pass 02 = Memory test pass 03 = Memory test fail 04 = POST end: boot system 05 = JMP doubleword pointer with EOI 06 = Protected tests pass 07 = Protected tests fail 08 = Memory size fail 09 = INT 15h Block Move 0A = JMP doubleword pointer without EOI 10 1 Byte Diskette Drive Types Bits 7-4 = Diskette drive 0 type 0000b = No drive 0001b = 360K drive 0010b = 1.2 MB drive 0011b = 720K drive 0100b = 1.44 MB drive Bits 3-0 = Diskette drive 1 type 11 1 Byte Reserved 12 1 Byte Fixed Disk Drive Types (0 = no drive) Bits 7-4 = Fixed Disk drive 0 type Bits 3-0 = Fixed Disk drive 1 type NOTE: These drive types do not necessarily correspond with the values stored at locations 19h and 1Ah. 13 1 Byte Reserved 14 1 Byte Equipment installed Bits 7-6 = Number of diskette drives 00b = 1 Diskette drive 01b = 2 diskette drives Bits 5-4 = Primary display 00b = Reserved 01b = 40x25 color 10b = 80x25 color 11b = 80x25 monochrome Bits 3-2 = Reserved Bit 1 = 1 Math coprocessor installed Bit 0 = 1 Diskette drive installed 15 1 Byte Base memory in 1K, low byte 16 1 Byte Base memory in 1K, high byte 17 1 Byte Expansion memory size, low byte 18 1 Byte Expansion memory size, high byte 19 1 Byte Fixed disk drive 0 type 1A 1 Byte Fixed disk drive 1 type 1B-2D 19 Bytes Reserved 2E 1 Byte Configuration information checksum--high byte 2F 1 Byte Configuration information checksum--low byte 30 1 Byte Actual expansion memory size--low byte 31 1 Byte Actual expansion memory size--high byte 32 1 Byte Century in BCD 33 1 Byte Information flag Bit 7 = 1 128 KByte expanded memory is present Bit 6 = 1 Setup flag (?) Bits 5-0 = Reserved 34-3F 12 Bytes Reserved