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Hardware Oddity Combiner Legalization
Evidence: NVIDIA vendor implementation history, not yet an Xbox measurement. The NV_register_combiners issues and revision history explains that an earlier specification prohibited combining certain dot-product outputs with the summed output. Hardware could perform it, the driver never rejected it, applications used it, and the specification was changed.
The same API text avoids guaranteeing exact arithmetic precision. Its mention of NV10 nine-bit signed fixed-point arithmetic is not proof that every NV2A intermediate has that format.
Proposed test: submit the historically prohibited combination through raw NV2A state and compare outputs. Pair it with precision-sensitive payload shaders, such as combiner-dependent bit packing, to locate packing, rounding, and clamp points.
See also NV2A Graphics Architecture.
DSP tooling guide and navigation updated November 2, 2026 for experimental PR #384, source 8f51d237. Capture/replay usage and limits.
The earlier wiki-wide review was published November 1, 2026. Emulator source: b7140848. Reviewed wiki content: 1d2b671. Current status · Release availability · Publication process.
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