emu860.py -- an i860 interpreter (reuses the dis860 decoder) that executes the
real Division firmware. This is the foundation of the preservation-grade
emulator (run the board's own code, vs the GL bridge which interprets the wire).
- Boots VREND.MNG cleanly: i860 init (psr/dirbase/fsr), enables the MMU, then
idle-spins at 0xf0400590 waiting for a transputer interrupt (init complete).
Board-config regs modelled (0xfffff720=2, 0xfffff70c=1) via map_control().
- Call harness (cpu.call): invoke firmware functions directly, bypassing the
(un-emulated) transputer that normally drives the CCB.
- Correct memory map: .data/.bss linked LOW (DATA_BASE=0), so globals resolve.
- FP unit with double precision (register pairs): fadd/fsub/fmul/famov/frcp/
frsqr/fix/ftrunc/fgt/feq/fxfr/fiadd/fisub.
- Delay slots, control regs, sparse MMIO memory with trap/logging, tail-trace
and stopat debug aids.
draw_scene now runs real code (incl. a double int->float conversion) until it
needs accumulated scene state -- next step is replaying a captured wire command
sequence through the command dispatcher (jump table @0x47cb8) so the scene
builds and draw_scene emits the IGC coefficient stream (Tier-1 handoff).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5
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