Last Updated or created 2023-01-06
Don’t know bios passwd anymore?
o = out port 0x0070-0x0071 The CMOS and RTC registers (more info below) # Does not seem related but it works! -o 70 2E -o 71 FF -q OR -o 70 17 -o 71 17 -q
Other fixes i’ve used:
Remove cmos battery .. and short the connections with wire.
This CAN completely reset your Bios settings!
0070-007F ---- CMOS RAM/RTC (Real Time Clock MC146818) 0070 w CMOS RAM index register port (ISA, EISA) bit 7 = 1 NMI disabled = 0 NMI enabled bit 6-0 CMOS RAM index (64 bytes, sometimes 128 bytes) any write to 0070 should be followed by an action to 0071 or the RTC wil be left in an unknown state. 0071 r/w CMOS RAM data port (ISA, EISA) RTC registers: 00 current second in BCD 01 alarm second in BCD 02 current minute in BCD 03 alarm minute in BCD 04 current hour in BCD 05 alarm hour in BCD 06 day of week in BCD 07 day of month in BCD 08 month in BCD 09 year in BCD (00-99) 0A status register A bit 7 = 1 update in progress bit 6-4 divider that identifies the time-based frequency bit 3-0 rate selection output frequency and int. rate 0B status register B bit 7 = 0 run = 1 halt bit 6 = 1 enable periodic interrupt bit 5 = 1 enable alarm interrupt bit 4 = 1 enable update-ended interrupt bit 3 = 1 enable square wave interrupt bit 2 = 1 calendar is in binary format = 0 calendar is in BCD format bit 1 = 1 24-hour mode = 0 12-hour mode bit 0 = 1 enable daylight savings time. only in USA. useless in Europe. Some DOS versions clear this bit when you use the DAT/TIME command. 0C status register C bit 7 = interrupt request flag bit 6 = peridoc interrupt flag bit 5 = alarm interrupt flag bit 4 = update interrupt flag bit 3-0 reserved 0D status register D bit 7 = 1 Real-Time Clock has power bit 6-0 reserved 0E diagnostics status byte bit 7 = 0 RTC lost power bit 6 = 1 CMOS RAM checksum bad bit 5 = 1 invalid configuration information at POST bit 4 = 1 memory size error at POST bit 3 = 1 fixed disk/adapter failed initialization bit 2 = 1 CMOS RAM time found invalid bit 1 = 1 adapters do not match configuration (EISA) bit 0 = 1 time out reading an adapter ID (EISA) 0F shutdown status byte 00 = normal execution of POST 01 = chip set initialization for real mode reentry 04 = jump to bootstrap code 05 = issue an EOI an JMP to Dword ptr at 40:67 06 = JMP to Dword ptrv at 40:67 without EOI 07 = return to INT15/87 (block move) 08 = return to POST memory test 09 = return to INT15/87 (block move) 0A = JMP to Dword ptr at 40:67 without EOI 0B = return IRETS through 40:67 10 diskette drive type for A: and B: bit 7-4 drive type of drive 0 bit 3-0 drive type of drive 1 = 0000 no drive = 0001 360K = 0010 1M2 = 0011 720K = 0100 1M44 = 0101-1111 reserved 11 reserved / AMI Extended CMOS setup (AMI Hi-Flex BIOS) bit 7 = 1 Typematic Rate Programming bit 6-5 = 00 Typematic Rate Delay 250 mSec bit 4-0 = 00011 Typematic Rate 21.8 Chars/Sec 12 fixed disk drive type for drive 0 and drive 1 bit 7-4 drive type of drive 0 bit 3-0 drive type of drive 1 if either of the nibbles equals 0F, then bytes 19 an 1A are valid 13 reserved / AMI Extended CMOS setup (AMI Hi-Flex BIOS) bit 7 = 1 Mouse Support Option bit 6 = 1 Above 1 MB Memory Test disable bit 5 = 1 Memory Test Tick Sound disable bit 4 = 1 Memory Parity Error Check enable bit 3 = 1 Hit <ESC> Message Display disabled bit 2 = 1 Hard Disk Type 47 Data Area at address 0:300 bit 1 = 1 Wait For <F1> If Any Error enabled bit 0 = 1 System Boot Up Num Lock is On 14 equipment byte bit 7-6 diskette drives installed = 00 1 drive installed = 01 2 drives installed = 10 reserved = 11 reserved bit 5-4 primary display = 00 adapter card with option ROM = 01 40*25 color = 10 80*25 color = 11 monochrome bit 3-2 reserved bit 1 = 1 coprocessor installed (non-Weitek) bit 0 diskette drive avaliable for boot 15 LSB of systemn base memory in Kb 16 MSB of systemn base memory in Kb 17 LSB of total extended memory in Kb 18 MSB of total extended memory in Kb 19 drive C extension byte 1A drive D extension byte 1B-27 reserved 1B/1C word to 82335 RC1 roll compare register at  (Phoenix) 1D/1E word to 82335 RC2 roll compare register at  (Phoenix) 28 HP-Vectra checksum over 29-2D 29-2D reserved 29/2A word to Intel 82335 CC0 compare register at (Phoenix) 2B/2C word send to 82335 CC1 compare register at [2A] (Phoenix) 2D AMI Extended CMOS setup (AMI Hi-Flex BIOS) (Phoenix BIOS checks for the values AA or CC) bit 7 = 1 Weitek Processor Absent bit 6 = 1 Floppy Drive Seek At Boot disabled bit 5 = 1 System Boot Up Sequence C:, A: bit 4 = 1 System Boot Up Speed is high bit 3 = 1 Cache Memory enabled bit 2 = 1 Internal Cache Memory <1> bit 1-0 reserved 2E CMOS MSB checksum over 10-2D 2F CMOS LSB checksum over 10-2D 30 LSB of extended memory found above 1Mb at POST 31 MSB of extended memory found above 1Mb at POST 32 date century in BCD 33 information flags bit4 = bit4 from CPU register CR0 (Phoenix) this bit is only known as INTEL RESERVED 34-3F reserved 34 bit4 bit5 (Phoenix BIOS) 3D/3E word to 82335 MCR memory config register at (Phoenix) 3D bit3 base memsize 512/640 (Phoenix) 3E bit7 = 1 relocate enable (Phoenix) bit1 = 1 shadow video enable (Phoenix) bit0 = 1 shadow BIOS enable (Phoenix) User Definable Drive Parameters are also stored in CMOS RAM: AMI (386sx BIOS 1989) first user definable drive (type 47) 1B L cylinders 1C H cylinders 1D heads 1E L Write Precompensation Cylinder 1F H Write Precompensation Cylinder 20 ?? 21 L cylinders parking zone 22 H cylinders parking zone 23 sectors AMI (386sx BIOS 1989) second user definable drive (type 48) 24 L cylinders 25 H cylinders 26 heads 27 L Write Precompensation Cylinder 28 H Write Precompensation Cylinder 29 ?? 2A L cylinders parking zone 2B H cylinders parking zone 2C sectors Phoenix (386BIOS v1.10.03 1988) 1st user definable drv (type48) 20 L cylinders 21 H cylinders 22 heads 23 L Write Precompensation Cylinder 24 H Write Precompensation Cylinder 25 L cylinders parking zone 26 H cylinders parking zone 27 sectors Phoenix (386BIOS v1.10.03 1988) 2nd user definable drv (type49) (when PS/2-style password option is not used) 35 L cylinders 36 H cylinders 37 heads 38 L Write Precompensation Cylinder 39 H Write Precompensation Cylinder 3A L cylinders parking zone 3B H cylinders parking zone 3C sectors