{ > Could someone please post what each of the 64 bytes of the CMOS are. I > know how to read/write to the CMOS but do not know whitch byte is what. I don't think this one is complete, but here you go: Offset Hex Size (bytes) Description ========== ============ =========== 00h 1 Current second in BCD 01h 1 Alarm second (BCD) 02h 1 Current minute (BCD) 03h 1 Alarm minute (BCD) 04h 1 Current hour (BCD) 05h 1 Alarm hour (BCD) 06h 1 Current day of week (BCD) 07h 1 Current day (BCD) 08h 1 Current month (BCD) 09h 1 Current year (BCD) 0Ah 1 Status register A Bit 7 = Update in progress 0 = date & time can be read 1 = time update busy Bit 6-4 = Time frequency divider 010 = 32.768 KHz Bit 3-0 = Rate selection frequency 0110 = 1.024 KHz sq. wve. freq. 0Bh 1 Status register B Bit 7 = Clock update cycle 0 = Update normally 1 = Abort update in progress Bit 6 = Periodic interrupt 0 = disable (default), 1 = enable Bit 5 = Alarm interrupt 0 = disable (default), 1 = enable Bit 4 = Update-ended interrupt 0 = disable (default), 1 = enable Bit 3 = Status register A sq. wve. freq. 0 = disable (default), 1 = enable Bit 2 = Date format 0 = Calender in BCD format (default) 1 = Calender in binary format Bit 1 = 24-hour clock 0 = 24-hour, 1 = 12-hour Bit 0 = Daylight Savings Time 0 = disable (default), 1 = enable 0Ch 1 Status register C Bit 7 = IRQF flag Bit 6 = PF Flag Bit 5 = AF Flag Bit 4 = UF Flag Other bits reserved 0Dh 1 Status register D Bit 7 = Valid CMOS RAM bit 0 = battery dead, 1 = battery OK Other bits reserved 0Eh 1 Diagnostic status Bit 7 = Real-time clock power status 0 = OK, 1 = not OK Bit 6 = CMOS checksum status 0 = good, 1 = bad Bit 5 = POST config. status 0 = valid, 1 = not valid Bit 4 = POST Memory size check 0 = OK, 1 = !OK Bit 3 = Fixd disk/adapter init. 0 = init OK, 1 = init bad Bit 2 = CMOS time status 0 = OK, 1 = !OK Other bits reserved 0Fh 1 Shutdown code 00h = Power on or soft reset 04h = POST end; boot system 05h = JMP dword ptr with EOI 06h = Prot. mode tests OK 07h = Prot. mode tests FAILED 08h = Memory size FAILED 09h = int 15h block move 0Ah = JMP dword ptr with EOI 0Bh = Used by 80386 10h 1 Floppy drive types Bits 7-4= Drive 0 type Bits 3-0= Drive 1 type (0000 = none, 0001 = 360K, 0010 = 1.2M, 0011 = 720K, 0100 = 1.44M, 0101 = 2.88K?) 11h 1 Reserved 12h 1 HD types Bits 7-4= Drive 0 type (0-15) Bits 3-0= Drive 1 type (0-15) 13h 1 Reserved 14h 1 Installed equipment Bits 7-6= Number of floppy drives Bits 5-4= Primary display 00= Adapter BIOS 01= CGA 40 cols 10= CGA 80 cols 11= MDA Bits 3-2= Reserved Bit 1 = Math copro. present Bit 0 = Floppy drive present 15h 1 Base memory low-order byte 16h 1 Base memory high-order byte 17h 1 Ext. mem. low-order byte 18h 1 Ext. mem. high-order byte 19h 1 Hard disk 0 extended type (0-255) 1Ah 1 Hard disk 1 ext. type (0-255) 1Bh 9 Reserved 2Eh 1 CMOS checksum high order byte 2Fh 1 CMOS checksum low order byte 30h 1 Actual extended memory low-order byte 31h 1 Actual extended memory high-order byte 32h 1 Date century in BCD 33h 1 POST information flag Bit 7 = Top 128K base memory status 0 = not installed 1 = installed Bit 6 = Setup program flag 0 = Normal (default) 1 = Output user message Other bits reserved 34h 2 Reserved