Put the container on the chip, and find the held bus costs 463 times the seam

ROADMAP P6c, FINDINGS 68. 78,125 B of a DLXP2's audio out of channel 3,
sample-exact, while the video channel fetches records off the same disc.

The two pieces 67.6 said were missing: the lump buffer (pg_afill/pg_afetch,
three slots and the minimum is unmeasured) and 67.2's remainder accumulator
(pg_apay). The capture prices what the accumulator avoided at 1.26 s of
lip-sync over the game, against 67.2's predicted 1.25.

The finding is the third piece, which nothing had named: the MSM6258 has no
starvation state, so the gap between a channel counting out and the next arm
is a held nibble pair driving the predictor. Stealing, the seam is 0.51 ms
over ten seconds because dma.i's new DM_HOOK services the chip from inside
the transfer wait -- 250,000 of 250,240 looks. Held, the 68000 is halted and
gets 369: every one of the ten lump boundaries has a seam, worst 72.8 ms,
2.31% of the audio. Identical bytes, different sound. 64.3 reaching the audio.

Two bugs, and no counter in the player could see either. Clearing DM_BARV does
not unchain a channel -- OCR bits 3-2 are what it obeys -- and the symptom is
POLL TIMEOUT on the lump and every record after it. And the refill ran one lump
ahead of its ring and overwrote the buffer the channel was reading: 11 of 11
armed, 11 fetched, no starve, and the sound wrong from 0.2 s in. Which is why
the gate is a WAV: verify_packed_audio.py walks the stream one delivered byte
at a time, because MAME's okim6258 resets the nibble select on every write and
a byte is two nibbles only 99.994% of the time.

check.sh ALL GREEN before (tmp/check_s36_start.log) and after
(tmp/check_s36_end.log), with the new stage.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6

docs/ROADMAP.md

@@ -129,9 +129,26 @@ minutes**. The payload is a remainder, `acc += 11*15625; n = acc//24; acc %= 24`
 which is `clock.i`'s shape for `clock.i`'s reason and the **third** time this
 tree has met the pattern. The four ADPCM axes ride in the header and the gate
 flips each one to prove they earn it (**order −31.99 dB, formula −24.86**). The
-wire is **589.6 KB/s**, 65.3's figure to the tenth. **What is left of P6 is the
+wire is **589.6 KB/s**, 65.3's figure to the tenth. ~~**What is left of P6 is the
 last quarter: no audio has been played out of this container on any layer, and
-two DMA channels have never run at once.**
+two DMA channels have never run at once.**~~
+
+Amended end of session 36: **P6c IS DONE, AND HOLDING THE BUS COSTS THE AUDIO
+463x THE SEAM (FINDINGS 68).** All 78,125 B of the container's audio reached the
+chip, in order, sample-exact against the four axes in its own header, out of a
+player that was fetching records off the same disc at the same time. **Two DMA
+channels have now run at once and the interaction is not in the bytes, it is in
+the timing**: the MSM6258 has no starvation state, so the interval between a
+channel counting out and the CPU arming the next lump is a held nibble pair
+driving the predictor. Stealing, the seam is **0.51 ms over ten seconds**;
+**held, it is 236 ms — 2.31% of the audio, every one of the ten lump boundaries,
+worst 72.8 ms**, because a burst channel halts the 68000 and the only place a
+68000 driving this video path has time is inside the transfer wait (250,000 of
+250,240 service calls). That is FINDINGS 64.3 reaching the audio: **the held
+configuration cannot feed a second consumer**, and B1's answer now decides a
+sound as well as a picture. 67.2's drift is measured rather than derived —
+predicted 1.25 s, played **1.26 s**. **What is left of P6 is the level (66.3)
+and the refill climb with a second consumer through a real branch point.**
 
 **THE COMPLETION TARGET IS M3, THE VERTICAL SLICE** (USER DECISION): one scene
 tree — a decision point, two outcomes, a death clip — with audio, streaming from
@@ -774,12 +791,18 @@ unchanged (F=11, A=14, 589.6 KB/s) and the **payload** did not: a lump's audio i
 7,161 or 7,162 B of a 7,168 B sector run, and feeding the chip the whole lump
 drifts 1.25 s over the game.
 
-**P6c. AUDIO OUT OF THE CONTAINER, ON THE MACHINE (new, session 35).** Every
+**P6c. AUDIO OUT OF THE CONTAINER, ON THE MACHINE. DONE, session 36 — FINDINGS
+68.** The lump buffer is `PG_ABUF` (three slots, prefill two, and the minimum
+depth is still unmeasured), the remainder accumulator is `pg_apay`, and the
+service runs from inside `dma.i`'s transfer wait through `DM_HOOK` because once
+a frame is a 90 ms seam by construction. **Two channels have run at once**: the
+bytes are identical in both DMAC configurations and the sound is not — held
+costs 236 ms of replayed byte against stealing's 0.51 ms. ~~Every
 piece exists and none is joined up. The container carries the bytes (67); the
 transport is `src/player/adpcm.i`'s channel-3 configuration, which is the IPL
 ROM's own and worked first time (66.1). What is missing is **the lump buffer**
 — 14,336 B, double-buffered, allocated by nobody — and **the remainder
-accumulator**, which is three instructions and is not optional.
+accumulator**, which is three instructions and is not optional.~~
 
 **And the interaction neither half has met: TWO CHANNELS AT ONCE.** The video
 channel holds the bus and halts the 68000, which already costs the frame clock
@@ -915,11 +938,13 @@ B2 blanking ─┬─ NOT blanked ─> K3's DMAC-DIRECT player is the one: 54.9%
 B1 BURST rate (NEW, 64.2) ──> which of the two K3/K4 wins, if B2 blanks
 
 P6 audio: encoder gated (65), P6a the chip's own decoder measured (66),
-  P6b DLXP2 written and gated, 589.6 KB/s on the wire (67)
-  └─> P6c AUDIO OUT OF THE CONTAINER ─┬─ the bytes exist, the transport
-      needs no board: the transport   │  exists, the lump buffer does not
-      is the IPL ROM's own (66.1)     └─> TWO CHANNELS AT ONCE, which is
-                                         the one thing nothing has run
+  P6b DLXP2 written and gated, 589.6 KB/s on the wire (67),
+  P6c PLAYED -- 78,125 B to the chip beside the video channel (68)
+  └─> and the second consumer is now ANOTHER INPUT TO B1/B2:
+      stealing -> 0.51 ms of seam over 10 s      \  same bytes,
+      held     -> 236 ms, every lump boundary    /  different sound
+  └─> what is LEFT of P6: the LEVEL (66.3, oldest open item) and the
+      refill climb with the second consumer through a branch point
 ```
 
 **Read that top-left branch as the project's live question.** Everything else