If an error occurs prior to the screen becoming initialised, then the screen cannot display the error message. Systems with a Phoenix BIOS will then generate BEEP CODES, which may be used to identify a POST error that occurs when the screen is not available.
| Beep Code | Description |
|---|---|
| 1 1 3 | CMOS read/write failure |
| 1 1 4 | ROM BIOS checksum error |
| 1 2 1 | Programmable interval timer failure |
| 1 2 2 | DMA initialisation failure |
| 1 2 3 | DMA page register read/write failure |
| 1 3 1 | RAM refresh verification failure |
| 1 3 3 | First 64k RAM chip or data line failure |
| 1 3 4 | First 64k RAM odd/even logic failure |
| 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 failure |
| 2 1 2 | Bit 1 first 64k RAM failure |
| 2 1 3 | Bit 2 first 64k RAM failure |
| 2 1 4 | Bit 3 first 64k RAM failure |
| 2 2 1 | Bit 4 first 64k RAM failure |
| 2 2 2 | Bit 5 first 64k RAM failure |
| 2 2 3 | Bit 6 first 64k RAM failure |
| 2 2 4 | Bit 7 first 64k RAM failure |
| 2 3 1 | Bit 8 first 64k RAM failure |
| 2 3 2 | Bit 9 first 64k RAM failure |
| 2 3 3 | Bit 10 first 64k RAM failure |
| 2 3 4 | Bit 11 first 64k RAM failure |
| 2 4 1 | Bit 12 first 64k RAM failure |
| 2 4 2 | Bit 13 first 64k RAM failure |
| 2 4 3 | Bit 14 first 64k RAM failure |
| 2 4 4 | Bit 15 first 64k RAM failure |
| 3 1 1 | Slave DMA register failure |
| 3 1 2 | Master DMA register failure |
| 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 initialisation failure |
| 3 4 1 | Screen retrace test failure |
| 3 4 2 | Search for video ROM in progress |
NOTE: "low" means a lower-pitched beep precedes the three bursts.
| Beep Codes | Description |
|---|---|
| 4 2 1 | Timer tick interrupt in progress or failure |
| 4 2 2 | Shutdown test in progress or failure |
| 4 2 3 | Gate A20 failure |
| 4 2 4 | Unexpected interrupt in protected mode |
| 4 3 1 | RAM test in progress or failure>ffffh |
| 4 3 3 | Interval timer channel 2 test or failure |
| 4 3 4 | Time of Day clock test failure |
| 4 4 1 | Serial port test or failure |
| 4 4 2 | Parallel port test or failure |
| 4 4 3 | Math coprocessor test or failure |
| low 1 1 2 | System Board select failure |
| low 1 1 2 | Extended CMOS RAM failure |