Post Codes

The Xbox 360 uses Post Codes to report the current step of the boot process. They can be read using 8 post points on the bottom of the motherboard which form a hex byte.

Post Codes List

The "Possible Cause" indicates possible reasons for post code if the unit is displaying an error code on the front panel or hanging on boot.

1BL

Not applicable to Waternoose DD1, Shiva, or when Secure ROM is not used.

Hex	Name	Description	Possible Cause
0x10	BEGIN	1BL entry point
0x11	FSB_CONFIG_PHY_CONTROL	FSB function 1	FSB fail
0x12	FSB_CONFIG_RX_STATE	FSB function 2	FSB fail
0x13	FSB_CONFIG_TX_STATE	FSB function 3	FSB fail
0x14	FSB_CONFIG_TX_CREDITS	FSB function 4	FSB fail
0x15	FETCH_OFFSET	Fetch 2BL offset in flash	GPU, SB, Nand
0x16	FETCH_HEADER	Fetch 2BL header from flash
0x17	VERIFY_HEADER	Verify 2BL header	Bad 2BL header
0x18	FETCH_CONTENTS	Copy 2BL to SRAM	Bad nand image
0x19	HMACSHA_COMPUTE	Compute 2BL HMAC hash
0x1A	RC4_INITIALIZE	Initialize 2BL RC4
0x1B	RC4_DECRYPT	Decrypt 2BL	Bad nand image
0x1C	SHA_COMPUTE	Compute 2BL hash
0x1D	SIG_VERIFY	Verify 2BL hash	Bad 2BL signature
0x1E	BRANCH	Branch to 2BL

2BL

Later retail systems uses a split 2BL which added the CB_A and renamed the CB to CB_B. Earlier units and developer systems use a single 2BL.

CB_A

Hex	Name	Description	Possible Cause
0xD0		CB_A entry point
0xD1	READ_FUSES	Read eFUSEs
0xD2	VERIFY_OFFSET_CB_B	Verify CB_B offset in flash	Bad nand image
0xD3	FETCH_HEADER_CB_B	Fetch CB_B header from flash
0xD4	VERIFY_HEADER_CB_B	Verify CB_B header	Bad CB_B header
0xD5	FETCH_CONTENTS_CB_B	Copy CB_B to SRAM	Bad nand image
0xD6	HMACSHA_COMPUTE_CB_B	Generate CB_B hash
0xD7	RC4_INTIALIZE_CB_B	Initialize CB_B RC4
0xD8	RC4_DECRYPT_CB_B	Decrypt CB_B	Bad nand image
0xD9	SHA_COMPUTE_CB_B	Compute CB_B hash
0xDA	SHA_VERIFY_CB_B	Verify CB_B hash	Bad CB_B signature
0xDB	BRANCH_CB_B	Branch to CB_B

CB/SB/CB_B

Hex	Name	Description	Possible Cause
0x20		2BL entry point, initialize SoC
0x21	INIT_SECOTP	Initialize Secure ROM and eFUSEs
0x22	INIT_SECENG	Initialize security engine
0x23	INIT_SYSRAM	Initialize system RAM	Bad GPU, RAM
0x24	VERIFY_OFFSET_3BL	Verify 3BL offset in flash	Bad nand image
0x25	LOCATE_3BL	Locate 3BL in flash	Bad nand image
0x26	FETCH_HEADER_3BL	Fetch 3BL header from flash
0x27	VERIFY_HEADER_3BL	Verify 3BL header	Bad 3BL header
0x28	FETCH_CONTENTS	Copy 3BL to SRAM	Bad nand image
0x29	HMACSHA_COMPUTE_3BL	Generate 3BL hash
0x2A	RC4_INITIALIZE_3BL	Initialize 3BL RC4
0x2B	RC4_DECRYPT_3BL	Decrypt 3BL	Bad nand image
0x2C	SHA_COMPUTE_3BL	Compute 3BL hash
0x2D	SHA_VERIFY_3BL	Verify 3BL hash	Bad 3BL signature
0x2E	HWINIT	Hardware initialization	Bad GPU, RAM
0x2F	RELOCATE	Relocate to system RAM
0x30	VERIFY_OFFSET_4BL	Verify 4BL offset in flash	Bad nand image
0x31	FETCH_HEADER_4BL	Fetch 4BL header from flash
0x32	VERIFY_HEADER_4BL	Verify 4BL header	Bad 4BL header
0x33	FETCH_CONTENTS_4BL	Copy 4BL to RAM	Bad nand image
0x34	HMACSHA_COMPUTE_4BL	Generate 4BL hash
0x35	RC4_INITIALIZE_4BL	Initialize 4BL RC4
0x36	RC4_DECRYPT_4BL	Decrypt 4BL	Bad nand image
0x37	SHA_COMPUTE_4BL	Compute 4BL hash
0x38	SIG_VERIFY_4BL	Verify 4BL hash	Bad 4BL signature
0x39	SHA_VERIFY_4BL	Verify 4BL hash	Bad 4BL signature
0x3A	BRANCH	Branch to 4BL
0x3B	PCI_INIT	Initialize PCI	1BL Panics Hex Name Description Possible Cause 0x81 MACHINECHECK Panic - Machine Check 0x82 DATA_STORAGE Panic - Data Storage 0x83 DATA_SEGMENT Panic - Data Segment 0x84 INSTRUCTION_STORAGE Panic - Instruction Storage 0x85 INSTRUCTION_SEGMENT Panic - Instruction Segment 0x86 EXTERNAL Panic - External CPU interrupt triggered 0x87 ALIGNMENT Panic - Alignment 0x88 PROGRAM Panic - Program Illegal instruction 0x89 FPU_UNAVAILABLE Panic - FPU Unavailable 0x8A DECREMENTER Panic - Decrementer 0x8B HYPERVISOR_DECREMENTER Panic - Hypervisor Decrementer 0x8C SYSTEM_CALL Panic - System Call 0x8D TRACE Panic - Trace 0x8E VPU_UNAVAILABLE Panic - VPU Unavailable 0x8F MAINTENANCE Panic - Maintenance 0x90 VMX_ASSIST Panic - VMX Assist 0x91 THERMAL_MANAGEMENT Panic - Thermal Management 0x92 WRONG_THREAD Panic - Wrong Thread 1BL executed on wrong thread 0x93 TOO_MANY_CORES Panic - Too Many Cores 1BL executer on wrong core 0x94 VERIFY_OFFSET Panic - Verify Offset Bad 2BL offset 0x95 VERIFY_HEADER Panic - Verify Header Bad 2BL header 0x96 SIG_VERIFY Panic - Signature Verify Bad 2BL signature 0x97 NONHOST_RESUME_STATUS Panic - Non Host Resume Status 0x98 NEXT_STAGE_SIZE Panic - Next Stage Size 2BL size too large 2BL Later retail systems uses a split 2BL which added the CB_A and renamed the CB to CB_B. Earlier units and developer systems use a single 2BL. CB_A Hex Name Description Possible Cause 0xF0 VERIFY_OFFSET_CB_B Panic - Verify Offset Bad CB_B offset 0xF1 VERIFY_HEADER_CB_B Panic - Verify Header Bad CB_B header 0xF2 SHA_VERIFY_CB_B Panic - Signature Verify Bad CB_B signature 0xF3 ENTRY_SIZE_INVALID_CB_B Panic - Entry Size Invalid CB_B size too large CB/SB/CB_B