Xbox 360 SMC Error: 0021


PCIE link did not enter L0 after seqUnReset time passed

This means the GPU to Southbridge PCIe bus was not able to be set up properly

  1. GPU Revision
    • There are many GPU models used on the 360s an incompatible GPU will cause the PCIe link to fail
    • Check that the GPU matches the correct model for the board:
      • Xenon, Zephyr_A: Y1 X02056 or X817791 (90nm GPU and eDRAM), Elpis X819195 (80nm GPU and eDRAM)
      • Zephyr_B: Y2 X02127 (80nm GPU and 90nm eDRAM)
      • Zephyr_C, Falcon: RHEA X810480, X816970, or X816971 (80nm GPU and eDRAM)
      • Jasper V1: Zeus X810478 or X817793 (65nm GPU and 80nm eDRAM)
      • Jasper Kronos: Kronos1 X820894 (65nm GPU and eDRAM)
      • Note: Kronos1 GPU does work on Jasper V1 if moved over

  2. PCIe Bus
    • Check all caps are 0.1uF (6.3V, X5R), and continuity from them to the other side of the PCIe trace
    • Most boards have test points on the other side of each trace to verify this
      • Xenon:
        • GPU Side: C4D1, C4D2, C4D3, and C5D1
        • Southbridge Side: C2C1, C2C2, C2C3, and C2C4
      • Zephyr, Falcon, Jasper:
        • GPU Side: C4D1, C4D2, C4D3, and C4D7
        • Southbridge Side: C2C1, C2C2, C2C3, and C2C4
      • Trinity:
        • GPU Side: C5E1, C5E2, C5E3, and C5E4
        • Southbridge Side: C3D2, C3E1, C3E2, and C3E3
      • Corona:
        • GPU Side: C5E1, C5E2, C5E3, and C5E4
        • Southbridge Side: C3D3, C3D4, C3D5, and C3D6

  3. PCIe Clock
    • Check that ANA_CLK_OE goes high (3.3V):
      • Phat: FT2P4
      • Trinity: FT3R13
      • Corona: Skip this step, signal not present
      • If missing signal, replace Southbridge:
        • Phat: U2C1
        • Slim: U3D1
    • Check junction between the sets of 33 and 49.9 Ohm resistors for proper 100 MHz differential clock
    • If bad/missing signal, check the values of the resistors as follows:
      • Xenon:
        • Check R3C6 and R3C10: 33 Ohms
        • Check R3C5 and R3C9: 49.9 Ohms
      • Zephyr, Falcon, Jasper:
        • Check R4B27 and R4C8: 33 Ohms
        • Check R3B5 and R3C9: 49.9 Ohms
      • Trinity:
        • Check R3B21 and R3C2: 33 Ohms
        • Check R3B20 and R3C1: 49.9 Ohms
      • Corona
        • PCIe Clock is internal to the Southbridge, but there are test points
        • Check R3D28 and R2D29: 10K Ohms
        • Test Points: DB3R6 and DB3R7
    • If still bad/missing clock signal, replace clockgen chip:
      • Xenon: Cypress CY28517 U3B4
      • Zephyr, Falcon, Jasper: HANA U4C2
      • Trinity: HANA U3B1
      • Corona: Southbridge U3D1

  4. Southbridge or GPU
    • If everything so far is fine, Southbridge or GPU is likely at fault
    • There is no reliable way to tell which chip is at fault
    • It is recommended to replace Southbridge first:
      • Phat: U2C1
      • Slim: U3D1
    • If all else fails, replace GPU:
      • Phat: U4D1
      • Slim: U5E1