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31250 bench run: wedge patch holds under retry storm; window is byte-scaled

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127s mash at 31250: zero wedges — but 5655 framing resyncs, duplicate
replies (215% of poll slots) and AbandonCount=65 reveal the board's
reply ACK-wait scales with byte time: ~5+ms at 9600 (USB beats it,
zero framing) vs ~1.6ms at 31250 (USB cannot). All 65 retry
exhaustions self-recovered through the patched give-up path — the
strongest field proof of the latch fix yet; unpatched firmware would
have wedged on the first. Verdict recorded in ANALYSIS.md: cabinets
run the 9600 patched chip; 31250 stays a bench branch until the retry
window is widened in firmware.

Tool: before-snapshot now retries once (can lose the post-DTR boot
race, as this run showed); evidence log archived.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Cyd
2026-07-18 00:36:23 -05:00
co-authored by Claude Fable 5
parent d8cac8927a
commit 27a592da53
1 changed files with 24 additions and 0 deletions
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RIOv4_2-ANALYSIS.md
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@@ -240,3 +240,27 @@ heavier mash is decisive. Remaining (cabinet): overnight idle soak +
a native-game session. Both check snapshots also reported a board/lamp a native-game session. Both check snapshots also reported a board/lamp
fault item — persistent across chips, likely a real tired lamp; inspect fault item — persistent across chips, likely a real tired lamp; inspect
separately. separately.
## 31250-baud bench run (2026-07-18) — patch holds; retry window is byte-scaled
`testlogs/riomash-patched-31250-20260718-003114.log` (127s mash, FTDI
COM1 @ 31250, latency timer already 1ms): **zero wedges**, but
framing=5655, analog replies at 215% of poll slots (duplicates), and
AbandonCount=65 — a reply-retry storm. Reading: the board's reply
ACK-wait window scales with BYTE TIME, not wall clock. At 9600 the
window (~5+ms) hides USB turnaround entirely (zero framing in both
9600 runs); at 31250 it shrinks to ~1.6ms, which USB cannot reliably
beat, so most replies retransmit and 65 exhausted all 4 retries.
Two conclusions:
1. **Brutal confirmation of the wedge patch**: 65 trips through the
give-up path in 127s, every one self-recovered ($DFF0 stub). The
unpatched firmware would have latched dead on the first.
2. **31250 needs one more firmware tweak to be clean**: widen the
reply-retry wait (the pacing/limit around the $D90E/$D9BE retry
machine) so the window stays >=10ms of wall clock at 31250. Until
then: cabinets run the 9600 patched chip (validated clean); 31250
stays a bench branch. Note the duplicate replies also mean the raw
reply rate overstates throughput — unique samples are still capped
by the host's 55ms poll; harvesting the speed needs a faster poll
AFTER the retry window is fixed.