| IBM | AMI |
| PHOENIX | DKT/ERSO XT BIOS |
| MR BIOS | MYLEX 386 System BIOS |
| Beep(s) | Device |
| 1 short beep | System Okay |
| 2 short beeps | POST Error displayed on screen |
| Repeating short beeps | Power supply, system boards |
| 3 long beeps | 3270 keyboard card |
| 1 long, 1 short beep | System board |
| 1 long, 2 short beeps | Display adapter (MDA, CGA) |
| 1 long, 3 short beeps | EGA |
| Continuous beep | Power supply, system board |
| Beep(s) | Device |
| 1 short | Failure |
| 2 short | DRAM refresh |
| 3 short | Parity circuit |
| 4 short | Base 64K RAM |
| 5 short | Processor |
| 6 short | Keyboard controller gate A20 error |
| 7 short | Virtual mode exception error |
| 8 short | Display memory read/write test |
| 9 short | ROM BIOS checksum |
| 1 long, 3 short | Non-Fatal -- Conventional/extended memory |
| 1 long, 8 short | Non-Fatal -- Display/retrace test |
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PHOENIX
Fatal Errors
| Beep(s) | Device |
| 1-1-3 | CMOS or Realtime clock read/write |
| 1-1-4 | ROM BIOS checksum |
| 1-2-1 | Programmable interval timer |
| 1-2-2 | DMA initialization |
| 1-2-3 | DMA page register read/write |
| 1-2-4 | SRAM test and configuration |
| 1-3-1 | RAM refresh verification |
| 1-3-3 | 1st 64KB RAM odd/even logic |
| 1-4-1 | Address line failure first 64K RAM |
| 1-4-2 | Parity failure first 64K RAM |
| 2-1-1 | Bit 0 first 64K RAM |
| 2-1-2 | Bit 1 first 64K RAM |
| 2-1-3 | Bit 2 first 64K RAM |
| 2-1-4 | Bit 3 first 64K RAM |
| 2-2-1 | Bit 4 first 64K RAM |
| 2-2-2 | Bit 5 first 64K RAM |
| 2-2-3 | Bit 6 first 64K RAM |
| 2-2-4 | Bit 7 first 64K RAM |
| 2-3-1 | Bit 8 first 64K RAM |
| 2-3-2 | Bit 9 first 64K RAM |
| 2-3-3 | Bit 10 first 64K RAM |
| 2-3-4 | Bit 11 first 64K RAM |
| 2-4-1 | Bit 12 first 64K RAM |
| 2-4-2 | Bit 13 first 64K RAM |
| 2-4-3 | Bit 14 first 64K RAM |
| 2-4-4 | Bit 15 first 64K RAM |
| 3-1-1 | Slave DMA register |
| 3-1-2 | Master DMA register |
| 3-1-3 | Master interrupt mask register failure |
| 3-1-4 | Slave interrupt mask register failure |
| 3-2-4 | Keyboard controller test failure |
| 3-3-4 | Screen initialization |
| 3-4-1 | Screen retrace |
| 3-4-2 | Search for video RAM in process (not failure) |
Non-Fatal Errors
| Beep(s) | Device |
| 4-2-1 | Timer tick interrupt test (or in progress) |
| 4-2-2 | Shutdown test (or in progress) |
| 4-2-3 | Gate A20 failure |
| 4-2-4 | Unexpected interrupt in protected mode |
| 4-3-1 | RAM test in progress or address failure > FFFFh |
| 4-3-3 | Interval timer channel 2 (or test) |
| 4-3-4 | Time of day clock (or test) |
| 4-4-1 | Serial port (or test) |
| 4-4-2 | Parellel port (or test) |
| 4-4-3 | Math coprocessor (or test) |
| low 1-1-2 | System board select |
| low 1-1-3 | Extended CMOS Ram |
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DTK/ERSO XT BIOS
| Beep(s) | Device |
| 1 short | Begin POST and end POST |
| 1 long, 1 short | Floppy drive or controller failure |
| Continuous short | Parity error in first 64K RAM |
| Continuous tone | First 64K RAM failure |
| 1 long | Keyboard failed or locked, interrupt or other system board error |
| long short, long short, long short |
Video Initialization failure, or invalid video switch settings |
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MR BIOS
| Beep(s) | Code | Device |
| low high, low high low high high | 1A | Real time clock not updating |
| low high, low low low | 03 | ROM BIOS checksum test |
| low high, high low low | 04 | Page register test (ports 81-8F) |
| low high, low high low | 05 | 8042 keyboard controller selftest |
| low high, high high low | 07 | Memory refresh circuit test |
| low high, low low high | 08 | Master (16bit) DMA controller failure |
| low high, high low high | Slave (8bit) DMA controller failure | |
| low high, low low low low | 0A | Memory bank 0 pattern test failure |
| low high, high low low low | Memory bank 0 parity circuitry failure | |
| low high, low high low low | Memory bank 0 parity error | |
| low high, low low high low | Memory bank 0 data bus failure | |
| low high, high low high low | Memory bank 0 block access read failure | |
| low high, low high high low | Memory bank 0 block access read/write failure | |
| low high, high high high low | 0B | Master 8259 (port 21) failure |
| low high, low low low high | Slave 8259 (port A1) failure | |
| low high, high low low high | 0C | Master 8259 (port 20) interrupt address failure |
| low high, low high low high | Slave 8259 (port A0) interrupt address failure | |
| low high, high high low low | 8259 (port 20/A0) interrupt address failure | |
| low high, low low high high | Master 8259 (port 20) stuck intercept error | |
| low high, high low high high | Slave 8259 (port A0) stuck intercept error | |
| low high, low high high high | System timer 8254 CH0/IRQ0 Interrupt Failure | |
| low high, high high high high | 0D | 8254 channel 0 test and initialization |
| low high, low low low low high | 0E | 8254 Channel-2 (speaker) failure |
| low high, high low low low high | 8254 OUT2 (speaker detect) failure | |
| low high, low high low low high | 0F | CMOS RAM read/write test failure |
| low high, high high low low high | RTC periodic interrupt/IRQ8 failure | |
| low high, low low high low high | 10 | Video Initialization and (cold-boot) signon message |
| low high, high low high low high | 12 | Keyboard controller failure |
| low high, low low low high high | 17 | A20 Test failure due to 8042 timeout |
| low high, high low low high high | A20 gate stuck in disabled state | |
| low high, low high high low high | 19 | Memory parity error |
| low high, high high high low high | IO Channel Error |
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Mylex
386 System BIOS
| Beep(s) | Device |
| long | Begin POST beep code |
| 2 long | Video card bad or no video card |
| long, short, long | Keyboard controller error |
| long, 2 short, long | Keyboard error |
| long, 3 short, long | Programmable interrupt controller (8259-1) error |
| long, 4 short, long | Programmable interrupt controller (8259-1) error |
| long, 5 short, long | DMA page register error |
| long, 6 short, long | RAM Refresh error |
| long, 7 short, long | RAM data test error |
| long, 8 short, long | RAM parity error |
| long, 9 short, long | DMA Controller 1 error |
| long, 10 short, long | CMOS RAM failure |
| long, 11 short, long | DMA Controller 2 error |
| long, 12 short, long | CMOS RAM Battery Failure |
| long, 13 short, long | CMOS Checksum failed |
| long, 14 short, long | BIOS ROM checksum failed |
| several long beeps | Multiple failures |