The gallery example loaded but the Z80 never visibly ran: the screen stayed
frozen on garbage. Two multi-chip async-load races, neither caught by the
existing headless tests (which drive RESET manually and attach the display
before boot):
1. RESET edge-vs-level race. The Z80 only left reset on the RISING edge of
RESET (a pin watch). In the browser the 7 chips instantiate asynchronously,
so the small power-on-reset chip releases RESET before the larger Z80 has
registered its watch -> the edge is lost and the CPU stays in reset forever.
Fix: on_clock samples the RESET level (hardware-accurate; RESET is
level-sensitive) so a missed edge self-corrects. An undriven RESET reads low,
so the CPU safely stays in reset until something drives it high.
Repro/guard: chipbus-galaksija-reset-race (race ordering must still boot).
2. Display-snoop load-order race. galaksija-display was a passive write-snoop;
the ROM paints the screen ONCE at boot then idles, so a display that comes up
late misses every write and shows stale content forever. A snoop cannot
recover writes it never saw. Fix: fold the screen into the RAM chip
(galaksija-ram-display) and render from the ACTUAL video RAM (0x2800-0x2BFF,
internal 0x0800 with A0-A12 wiring) on a ~30 fps timer - correct regardless
of load order, exactly how the real machine scans video RAM.
Repro/guard: chipbus-galaksija-display-snoop-race (late snoop shows nothing)
+ chipbus-galaksija-ram-display (renders even when first paint is post-boot).
The example now has 6 chips (RAM+display merged, gdisp dropped), 76 wires.
Verified live in the browser: boots to "@'READY", shows the ">" prompt, and
pressing A echoes ">A_" through keyboard -> Z80 -> video RAM -> display. The
full chipbus suite is 45/45.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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