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ERROR_GRAPHICS_DDCCI_INVALID_MESSAGE_CHECKSUM
Checksum failure proves the packet bytes cannot be trusted
ERROR_GRAPHICS_DDCCI_INVALID_MESSAGE_CHECKSUM means Windows received enough of a DDC/CI message to calculate its checksum, but the result differed from the checksum byte supplied by the monitor. The corruption may originate in monitor firmware, a display bridge, marginal cabling, or incorrect packet framing.
Capture the raw bytes and recompute the checksum without modifying source-address or length fields. Repeat the same read at a conservative interval and compare which bytes vary. A stable but wrong checksum suggests a deterministic implementation defect; changing corruption points toward transport integrity. Do not accept the current or maximum VCP value from a packet that failed validation.
Integrity evidence to collect
- Entire packet including source, length, command, payload, and checksum.
- Locally computed checksum and the monitor-supplied byte.
- Error rate over repeated identical requests.
- Cable, dock, KVM, and input path used during the transfer.
References
- Microsoft: checksum mismatch error definition
- ddcutil: DDC/CI packet transport
- Linux kernel: bus and packet-integrity fault examples
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