| Hex
Code | Name | Description |
| C0 | Turn Off Chipset Cache | OEM Specific-Cache control |
| 1 | ProcessorTest1 | Processor Status (1FLAGS) Verification. Tests the following processor status flags: carry, zero, sign, overflow, The BIOS sets each flag, verifies they are set, then turns each flag off and verifies it is off. |
| 2 | ProcessorTest2 | Read/Write/Verify all CPU registers except SS, SP, and BP with data pattern FF and 00. |
| 3 | Initialize Chips | Disable NMI, PIE, AIE, UEI, SQWV
Disable video, parity checking, DMA
Reset math coprocessor
Clear all page registers, CMOS shutdown byte
Initialize timer 0, 1, and 2, including set EISA timer to a known state
Initialize DMA controllers 0 and 1
Initialize interrupt controllers 0 and 1
Initialize EISA extended registers. |
| 4 | Test Memory Refresh Toggle | RAM must be periodically refreshed to keep the memory from decaying. This function ensures that the memory refresh function is working properly |
| 5 | Blankvideo, Initialize keyboard | Keyboard controller initialization |
| 6 | Reserved | - |
| 7 | Test CMOS Interface and Battery Status | Verifies CMOS is working correctly,
detects bad battery. |
| BE | Chipset Default Initialization | Program chipset registers with power on BIOS defaults. |
| C1 | Memory presence test | OEM Specific-Test to size on-board memory |
| C5 | Early Shadow | OEM Specific-Early Shadow enable for fast boot. |
| C6 | Cache presence test | External cache size detection |
| 8 | Setup low memory | Early chip set initialization
Memory presence test
OEM chip set routines
Clear low 64K of memory
Test first 64K memory |
| 9 | Early Cache Initialization | Cyrix CPU initialization
Cache initialization |
| A | Setup Interrupt Vector Table | Initialize first 120 interrupt vectors with SPURIOUS_INT_HDLR and initialize INT 00h-1Fh according to INT_TBL |
| B | Test CMOS RAM Checksum | Test CMOS RAM Checksum, if bad, or insert key pressed, load defaults. |
| C | Initialize keyboard | Detect type of keyboard controller (optional) Set NUM_LOCK status. |
| D | Initialize Video Interface | Detect CPU clock.
Read CMOS location 14h to find out type of video in use.
Detect and Initialize Video Adapter |
| E | Test Video Memory | Test video memory, write sign-on message to screen.
Setup shadow RAM - Enable shadow according to Setup. |
| F | Test DMA Controller 0 | BIOS checksum test.
Keyboard detect and initialization |
| 10 | Test DMA Controller 1 | - |
| 11 | Test DMA Page Registers | Test DMA Page Registers. |
| 12-13 | Reserved | - |
| 14 | Test Timer Counter 2 | Test 8254 Timer 0 Counter 2. |
| 15 | Test 8259-1 Mask Bits | Verify 8259 Channel 1 masked interrupts by alternately turning off and on the interrupt lines. |
| 16 | Test 8259-2 Mask Bits | Verify 8259 Channel 2 masked Interrupts by alternately turning off and on the interrupt lines. |
| 17 | Test Stuck 8259's Interrupt Bits | Turn off interrupts then verify no interrupt mask register is on. |
| 18 | Test 8259 Interrupt Functionality | Force an interrupt and verify the interrupt occurred. |
| 19 | Test Stuck NMI Bits (Parity/IO Check) | Verify NMI can be cleared. |
| 1A | | Display CPU clock |
| 1B-1E | Reserved | - |
| 1F | Set EISA Mode | If EISA non-volatile memory checksum is good, execute EISA initialization. If not, execute ISA tests an clear EISA mode flag. Test EISA Configuration Memory Integrity (checksum & communication Interface). |
| 20 | Enable Slot 0 | Initialize slot 0 (System Board). |
| 21-2F | Enable Slots 1-15 | Initialize slots 1 through 15. |
| 30 | Size Base and Extended Memory | Size base memory from 256K to 640K
and extended memory above 1MB. |
| 31 | Test Base and Extended Memory | Test base memory from 256K to 640K and extended memory above 1MB using various patterns.
NOTE: This test is skipped in EISA mode and can be skipped with ESC key in ISA mode |
| 32 | Test EISA Extended Memory | If EISA Mode flag is set then test EISA memory found in slots initialization. NOTE: This test is skipped in ISA mode and can be skipped with ESC key in EISA mode. |
| 33-3B | Reserved | - |
| 3C | Setup Enabled | - |
| 3D | Initialize & Install Mouse | Detect if mouse is present, initialize mouse, install interrupt vectors. |
| 3E | Setup Cache Controller | Initialize cache controller. |
| 3F | Reserved | - |
| BF | Chipset Initialization | Program chipset registers with Setup values
Display virus protect disable or enable |
| 40 | Initialize Floppy Drive & Controller | Initialize floppy disk drive controller and any drives. |
| 42 | Initialize Hard Drive & Controller | initialize hard drive controller and any drives. |
| 43 | Detect & Initialize Serial/Parallel Ports | Initialize any serial and parallel ports (also game port). |
| 44 | Reserved | - |
| 45 | Detect & Initialize Math Coprocessor | Initialize math coprocessor. |
| 46 | Reserved | - |
| 47 | Reserved | - |
| 48-4D | Reserved | - |
| 4E | Manufacturing POST Loop or Display Messages | Reboot if Manufacturing POST Loop pin is set. Otherwise display any messages (i.e., any non-fatal errors that were detected during POST) and enter Setup. |
| 4F | Security Check | Ask password security (optional). |
| 50 | Write CMOS | Write all CMOS values back to RAM and clear screen. |
| 51 | Pre-boot Enable | Enable parity checker
Enable NMI, Enable cache before boot. |
| 52 | Initialize Option ROMs | Initialize any option ROMs present from C8000h to EFFFFh. NOTE: When FSCAN option is enabled, ROMs initialize from C8000h to F7FFFh. |
| 53 | Initialize Time Value | Initialize time value in 40h: BIOS area. |
| 60 | Setup Virus Protect | Setup virus protect according to Setup |
| 61 | Set Boot Speed | Set system speed for boot |
| 62 | Setup NumLock | Setup NumLock status according to Setup |
| 63 | Boot Attempt | Set low stack Boot via INT 19h. |
| B0 | Spurious | If interrupt occurs in protected mode. |
| B1 | Unclaimed NMI | If unmasked NMI occurs, display
Press F1 to disable NMI, F2 reboot. |
| E1-EF | Setup Pages | E1- Page 1, E2 - Page 2, etc. |
| FF | Boot | - |
