ADR 0101: Matrix Scale Cell Layouts, HiF4 Scale Words, and CScale

Decision

Each Matrix-MX side independently selects scale group and carrier from its primary type. MX FP8/FP4 uses group 32 and E8M0. HiF4X2 uses group 64 and one raw U32 HiF4 scale word. HiF4X2 is added only to Matrix-MX input roles; ordinary Matrix and every GEMV form retain their existing type sets.

Local A scale is CUBE_M32 storage [M,G]. Local B scale is CUBE_M32 storage [N,G], while its semantic view remains BScale[g,n]. One E8M0 CellReg stores [32,4]; one U32 HiF4 CellReg stores [32,1]. Column/K repeat is fast and 32-row/N repeat is slow. A partial final group or row block is legal storage tail and is not an operand. Primary B remains CUBE_N8.

Shared scales remain ordinary Tiles with normalized A-scale [group_M,G] and B-scale [G,N]. TransA or TransB applies to the corresponding independently bound primary and scale after any B.SUBVIEW resolution, without persistent source mutation.

One HiF4 raw U32 scale word contains E6M2 in bits 7:0, E1_8 bits in 15:8, and E1_16 bits in 31:16. E6M2 00..FE is finite with exponent bias 48 and two fraction bits; FF is a legal quiet NaN. Group lane q adds E1_8[floor(q/8)] and E1_16[floor(q/4)] to the base exponent.

B.FPATR bit 9 is CScaleEn and bit 10 remains reserved. CScaleEn is legal only for FP32 TMATMUL.ACC and TMATMULMX.ACC. CScale is the final mathematical Local source, uses U8 CUBE_M32 [M,1], and may not alias D or an auxiliary output. It scales C by 2^-CScale[m,0] before reductions, activation, quantization, and destination conversion. Omission defaults CScaleEn to zero and preserves prior results. The maximum Matrix Local source count becomes nine.

Compatibility and protected behavior

B.FPATR bit 9 was reserved, so zero retains binary meaning and one becomes defined only for the accepted FP32 ACC forms. Bit 10 remains fixed zero. Primary A/C/D M16/M32 legality remains capped at one row block even though the generic M32 scale grid supports multiple row blocks. ADR-0100 group-M and inactive-PE behavior, ADR-0098 active-role range/generation behavior, distinct C/D, rollback, and atomic output publication remain unchanged.

Verification

Executable evidence covers MX G5/N33 and HiF4 multi-repeat CellReg order, partial tails, E6M2 00/FE/FF, decoded HiF4X2 Matrix-MX acceptance, ordinary Matrix rejection, decoded CScale success, and reserved/missing/surplus/alias/ opcode/accumulator-class rejection before effects.

Release impact

The B.FPATR accepted mask and Matrix-MX type applicability change the 0.58.4 candidate encoding fingerprint. No release manifest, tag, or publication is created by this decision.

The accepted encoded-form count remains 542. The reviewed scalar-plus-command fingerprint after assigning B.FPATR bit 9 is e62de1b044c5b45ff4019cd19e3f545d4222e1ef6a69d2c26f93bcb128d54fee.