Error Messages and Beep Codes
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4.3 Port 80h Power On Self Test (POST) Codes
During the POST, the BIOS generates diagnostic progress codes (POST codes) to I/O
port 80h. If the POST fails, execution stops and the last POST code generated is left
at port 80h. This code is useful for determining the point where an error occurred.
Displaying the POST codes requires a PCI bus add-in card, often called a POST card.
The POST card can decode the port and display the contents on a medium such as a
seven-segment display.
NOTE
In order to view POST codes on a diagnostic card inserted into a PCI slot, the BIOS
must be enabled to route POST codes to the PCI slots. The default setting is to route
them to the LPC debug header, as this is required to pass Windows 8 certification.
The following tables provide information about the POST codes generated by the BIOS:
Table 45 lists the Port 80h POST code ranges
Table 46 lists the Port 80h POST codes themselves
Table 47 lists the Port 80h POST sequence
NOTE
In the tables listed above, all POST codes and range values are listed in hexadecimal.
Table 45. Port 80h POST Code Ranges
Range Subsystem
0x00 – 0x05 Entering SX states S0 to S5.
0x10, 0x20, 0x30,
0x40, 0x50
Resuming from SX states. 0x10 – S1, 0x20 – S2, 0x30 – S3, etc.
0x08 – 0x0F Security (SEC) phase
0x11 – 0x1F PEI phase pre MRC execution
0x21 – 0x29 MRC Memory detection
0x2A – 0x2F PEI phase post MRC execution
0x31 – 0x35 Recovery
0x36 – 0x3F Platform DXE driver
0x41 – 0x4F CPU Initialization (PEI, DXE, SMM)
0x50 – 0x5F I/O Buses: PCI, USB, ISA, ATA etc. 0x5F is an unrecoverable error. Start with PCI.
0x60 – 0x6F BDS
0x70 – 0x7F Output Devices: All output consoles.
0x80 – 0x8F For future use
0x90 – 0x9F Input devices: Keyboard/Mouse.
0xA0 – 0xAF For future use
0xB0 – 0xBF
Boot Devices: Includes fixed media and removable media. Not that critical since
consoles should be up at this point.
0xC0 – 0xCF For future use
0xD0 – 0xDF For future use
0xF0 – 0xFF
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