NVIDIA HGX H100 SXM5 Tensor Core GPU Error SXid 63: H100 SXid 63 NVLink Error
SXid 63 designates an uncorrectable fatal hardware error on one or more NVLink4 interconnect links, typically caused by link retrain exhaustion, physical transceiver/pad degradation, or socket cold-solder/interposer micro-fractures, halting distributed NCCL training runs.
Hardware Diagnostic Matrix
Spec Ref #6a76f248Required 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
- Distributed training cluster hangs indefinitely during NCCL all-reduce or barrier synchronization
- dmesg / kernel log outputs: 'NVRM: Xid (PCI:0000:XX:00): 63, pid=..., SXid: 63, NVLink Error'
- nvidia-smi nvlink -s shows one or more links in 'Down' or 'Recovery' state with fatal CRC/replay errors
Root Causes & System Failure Modes
Differential pair physical trace or high-speed connector pad damage between SXM5 GPU and HGX baseboard base NVLink Switch
Insufficient torque or non-coplanar tension across the SXM5 heat sink and interposer socket causing intermittent 53.125 Gbps PAM4 signaling failure
NVSwitch fabric ASIC power rail instability or localized LDO voltage sag dropping below the required 0.85V core rail threshold
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
Cluster Isolation and Telemetry Extraction
Drain the node from the Slurm/Kubernetes scheduler. Collect NVIDIA bug report via 'nvidia-bug-report.sh' and query 'nvidia-smi nvlink -e -i <gpu_id>' to identify the specific degraded NVLink port numbers and fatal symbol error registers.
Software Topology Check and Fabric Manager Reset
Stop nvidia-fabricmanager. Check if errors clear on a warm link retrain using 'dcgmi diag -r 3'. If link training permanently fails at the physical layer (PHY), unrecoverable hardware degradation is confirmed.
Power Isolation, Reseating, and Torque Check
Power down the chassis and disconnect all 54V/12V DC power trays. Ground to the chassis. Remove the affected H100 module cold plate, inspect the SXM5 BGA pins and interposer socket for debris or bent spring contacts, clean using lint-free solvent swabs, reseat the GPU, and torque SXM screws in an X-pattern precisely to vendor specification.
Post-Remediation Bandwidth and Stress Verification
Power on the host, start nvidia-fabricmanager, and execute 'nccl-tests' (all_reduce_perf -b 8M -e 8G -f 2 -g 8). Verify full 900 GB/s bidirectional NVLink bandwidth with 0 replay or fatal CRC events across all 18 links.
Hardware Reset & Fault Clear Sequence
Controller ProcedurePrevention & Routine Maintenance Guidelines
- Maintain strict datacenter ambient intake temperatures below 25°C to limit thermal cycle fatigue on high-speed PAM4 silicon interconnects
- Enforce precise calibrated torque sequence using OEM screw guides during any GPU or cold-plate field service
Frequently Asked Diagnostic Questions
What does error code SXid 63 indicate on NVIDIA HGX H100 SXM5 Tensor Core GPU?
SXid 63 designates an uncorrectable fatal hardware error on one or more NVLink4 interconnect links, typically caused by link retrain exhaustion, physical transceiver/pad degradation, or socket cold-solder/interposer micro-fractures, halting distributed NCCL training runs. In engineering telemetry, it indicates h100 sxid 63 nvlink error requiring circuit verification.
What are the primary triggers causing error SXid 63?
Diagnostic bench telemetry isolates the following common root causes: Differential pair physical trace or high-speed connector pad damage between SXM5 GPU and HGX baseboard base NVLink Switch; Insufficient torque or non-coplanar tension across the SXM5 heat sink and interposer socket causing intermittent 53.125 Gbps PAM4 signaling failure; NVSwitch fabric ASIC power rail instability or localized LDO voltage sag dropping below the required 0.85V core rail threshold.
How do I reset and clear NVIDIA error SXid 63?
Perform a cold reset of the HGX baseboard via BMC IPMI ('ipmitool raw 0x30 ...' or power cycle chassis auxiliary rails), followed by restarting the host OS and running 'systemctl restart nvidia-fabricmanager'. 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.