Definition
A test fixture is a bench rig that lets a technician power and scan a single hashboard outside the miner so faults can be located precisely. The board slots into the fixture, which supplies controlled power and signalling, then runs a chip-by-chip scan that reports which ASICs respond, which are dead, and which are underperforming, along with the position of each fault on the board. This turns a vague "chain only finds X chips" symptom into an exact location to inspect and rework.
What it measures
Beyond a pass/fail per chip, modern fixtures expose the test points used in repair, signals such as CLK, CO, RI, BO, and RST that pass through the chip daisy chain, plus domain voltages like VDD0V8 and VDD1V2. By watching where a signal stops propagating or where a voltage reads abnormally, the operator pinpoints the first failing chip or a faulty voltage domain rather than guessing.
Why bench testing matters
Diagnosing inside an assembled miner is slow and ambiguous because cable, control-board, and power-supply issues all masquerade as board faults. A dedicated fixture isolates the hashboard, supports dozens of models, and gives repeatable, position-aware results, which is why it is core equipment in any serious repair workflow. Bitmain's own factory test fixtures formalise this process.
The test fixture acts on the leads found in the diagnostic output. See Kernel Log for the in-machine symptoms that send a board to the bench, and Chip Domain Bypass for a salvage technique sometimes applied to faults the fixture locates.
In Simple Terms
A test fixture is a bench rig that lets a technician power and scan a single hashboard outside the miner so faults can be located…