Module B04 · concept player
fp8 is not one format. Drag the byte and watch the same eight bits decode to two different numbers — AMD's FNUZ on CDNA 3, and NVIDIA's OCP E4M3 on Hopper.
AMD FNUZ · bias 8 · CDNA 3■
1.0
NVIDIA OCP E4M3 · bias 7 · Hopper■
1.0
Exact bit arithmetic, not a measurement. Both formats are E4M3: 1 sign bit, 4 exponent bits, 3 mantissa bits. Each format is exact IEEE-style exponent/mantissa arithmetic with its own bias and special-case rule — not a training-run observation. FNUZ's maximum, 240, and OCP's maximum, 448, both fall out of this arithmetic at their respective largest bytes, which is the check that the decoder is right. Moving a checkpoint between vendors is not a reinterpret-cast — B04 section 3 covers what to do instead.