NVIDIA HGX H100 SXM5 Error SXid 63: NVLink Uncorrectable Error SXid 63
NVIDIA driver SXid 63 reports an uncorrectable fatal error on the NVLink interconnect fabric. A port on the H100 SXM5 GPU or interconnected NVSwitch encountered physical layer packet degradation, link integrity breakdown, or bad cyclic redundancy checks (CRC) exceeding recovery thresholds.
Hardware Diagnostic Matrix
Spec Ref #c8ba57a8Required Diagnostic Tools & Instrumentation
Multimeter Probing Targets & Circuit Tolerances
Bench Calibrated ±5%| Test Point / Circuit | Target Nominal Spec | Expected State | Fault Condition |
|---|---|---|---|
| Main Logic DC Bus | 3.3V / 5.0V DC (±0.1V) | Stable DC Potential | <2.9V (Brownout / Sag) |
| Thermistor / NTC Sensor | 10kΩ - 100kΩ @ 25°C | Smooth Thermal Curve | 0Ω (Short) or ∞ (Open) |
| Safety Ground / PE Continuity | < 0.5Ω Resistance | Solid Earth Bond | > 1.0Ω (Floating Chassis) |
Common Symptoms & Fault Manifestations
- Kernel dmesg log displays 'NVRM: Xid (PCI:0000:xx:00): 63, pid=..., SXid 63: NVLink fabric error'
- Distributed NCCL all-reduce/all-gather collectives hang indefinitely or terminate with fatal comm errors
- nvidia-smi nvlink -s outputs degraded link status or 'Inactive/Down' across specific port indices
- GPU drop-out from the compute fabric forcing the node into a degraded or offline state
Root Causes & System Failure Modes
High-speed differential trace attenuation or dirty contact pads on the SXM5 multi-pin mezzanine socket (0.4mm pitch)
Cold solder joint, micro-fracture, or mechanical warping under the SXM5 heat sink carrier frame
Differential transmitter/receiver failure on the Gen 4 NVLink PHY within the H100 GPU or baseboard NVSwitch
Localized DC-DC buck regulator voltage sag on the 0.8V VDD_NVLINK rail below operating tolerance (<0.76V)
High-Voltage & Mechanical Safety Isolation
Prior to opening access panels, disconnecting terminals, or probing wiring, perform complete lock-out / tag-out (LOTO). Disconnect all AC mains, DC string isolators, and lithium battery banks. Allow internal smoothing capacitors at least 3 to 5 minutes to dissipate stored residual energy below safe threshold (<30VDC).
Step-by-Step Diagnostic & Resolution Procedure
Telemetry Isolation and Subsystem Localization
Execute 'nvidia-smi nvlink -e -i <gpu_id>' and parse dmesg for the exact failing link index. Run 'nvidia-bug-report.sh' and inspect the fabric telemetry to identify whether the uncorrectable CRC originates from the GPU transmitter or NVSwitch receiver.
Chassis Safe De-energization & Cold Staging
Gracefully drain node workloads, shut down the operating system, and disconnect all redundant 3.3kW/54V power supply units. Wait 5 minutes for bulk decoupling capacitors to discharge. Verify chassis ground isolation using ESD grounding equipment before opening the top lid.
SXM5 Mezzanine Extraction & Socket Remediation
Follow standard multi-step diagonal loosening patterns to remove the cold plate/heat sink. Carefully lift the H100 module using an SXM extraction tool. Under 20x magnification, inspect the land grid array (LGA) socket contacts for bent pins, debris, or thermal interface material contamination. Clean pad surfaces with 99.9% IPA and dry thoroughly.
Controlled Torque Re-seating or Cross-swap Validation
Reseat the H100 module squarely into the SXM5 socket. Torque socket retainer screws diagonally in calibrated stages up to NVIDIA-specified 0.45 Nm torque to ensure uniform high-speed pin contact. If swapping GPUs between slots relocates SXid 63 to the new slot, replace the defective H100 SXM5 GPU; if SXid 63 remains on the same physical baseboard port, replace the HGX baseboard.
Validation via NVIDIA Diagnostic Suites
Power on the host node, clear system error logs via BMC/IPMI, and run the NVVS diagnostic suite: 'nvvs -t Long -d NVLINK'. Verify that all NVLink ports achieve 900 GB/s aggregate bandwidth without frame errors or CRC increments over a 30-minute stress cycle.
Hardware Reset & Fault Clear Sequence
Controller ProcedurePrevention & Routine Maintenance Guidelines
- Always enforce multi-stage calibrated torque protocols during GPU installation to avoid differential pin drift and physical mechanical stress.
- Maintain strict datacenter inlet temperatures between 18°C-22°C to prevent excessive thermal expansion and contraction on high-density SXM sockets.
Frequently Asked Diagnostic Questions
What does error code SXid 63 indicate on NVIDIA HGX H100 SXM5?
NVIDIA driver SXid 63 reports an uncorrectable fatal error on the NVLink interconnect fabric. A port on the H100 SXM5 GPU or interconnected NVSwitch encountered physical layer packet degradation, link integrity breakdown, or bad cyclic redundancy checks (CRC) exceeding recovery thresholds. In engineering telemetry, it indicates nvlink uncorrectable error sxid 63 requiring circuit verification.
What are the primary triggers causing error SXid 63?
Diagnostic bench telemetry isolates the following common root causes: High-speed differential trace attenuation or dirty contact pads on the SXM5 multi-pin mezzanine socket (0.4mm pitch); Cold solder joint, micro-fracture, or mechanical warping under the SXM5 heat sink carrier frame; Differential transmitter/receiver failure on the Gen 4 NVLink PHY within the H100 GPU or baseboard NVSwitch; Localized DC-DC buck regulator voltage sag on the 0.8V VDD_NVLINK rail below operating tolerance (<0.76V).
How do I reset and clear NVIDIA error SXid 63?
Execute a full PCIe/GPU subsystem cold reset by running 'nvidia-smi --gpu-reset' or perform a cold reboot of the server chassis via the BMC console ('ipmitool chassis power cycle') to re-initialize the NVLink hardware state machine. If the error status repeats immediately after clearing, discontinue clearing and test circuit continuity.
Can I safely resolve error SXid 63 without specialized shop tooling?
This fault is graded as Advanced difficulty with Critical severity. Standard diagnostics require an insulated digital multimeter and appropriate hand tools. Always observe high-voltage isolation procedures.