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SDD
c06cf7096b
The skip gate reaches the root weave and stops: video RAM and the rendered
frame are byte-identical at frames 3000/10000/30000/45000/60000 (42 s -> 14
min), and all 4 MiB of main RAM is identical at every sample except one byte
that oscillates. The PC histogram is tight: entered at frame ~611, dominated
by 0x3FB30390/0x3FB30110.
Wall: DUART2 (0x0620000, keyboard/mouse) is unmodelled, so the read-only ISR
at 0x06200005 is served by the board write-back latch and returns the value
the OS wrote to the write-only IMR (0x0033). The OS's DUART dispatcher
(0x3FB43800) masks 0x66 -> 0x22, so it services a phantom interrupt that can
never clear, spinning in the channel handler 0x3FB42410 and queue routine
0x3FB300F0. Forcing only 0x06200005 to 0 reproduces the full DUART2-mapped
run byte-for-byte; with VT1200_DUART2=1 the Terminal Manager dialog box from
the reference video appears at frame 3000 and the machine runs on.
Defaults unchanged: no-env still reaches HOST PORT - 15, skip still reaches
the weave. New opt-in knobs VT1200_DUMP_{FRAME,RAM_FRAMES,VRAM_FRAMES} and
resolve_console.py; progress.lua untouched.