Full mechanical port of emu860.py's validated semantics: paged memory,
integer ISA, control flow with delayed branches + bc.t/bnc.t annul, DIM
tracking, and the complete FP model (pipes with per-entry result precision,
PFAM/PFMAM dual-op routing, fdest bypass, raw-retire fix/ftrunc, K/T loads).
Python keeps the hooks via a shim; the C loop returns at hook pcs.
Differential result vs the hook-aligned reference trace (ref_trace2):
139.7M steps/s (Python: 398K/s = 351x), 35.8M steps, 2195 hooks,
43/43 checkpoints matched (pc + step count + full reg CRC).
The original i860 ran ~40 MIPS: real-time geometry is cleared 3.5x over --
M4's gate (GPU-RETARGET.md) is open.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>