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
ROADMAP K3. src/player/packed.s (2,898 B) brings up its own display, builds
its own 193-entry DMA chain, keeps its own frame clock off V-DISP and fetches
every record itself with READ(10) off a CZ-6BS1. The rig writes no picture
byte, no palette entry and no CRTC register.
120 of 120 frames pixel-exact, every one compared, in both palette orders --
the gate had to grow to do it, because a packed frame is a LITERAL and the
codec's recursion was what made one comparison audit 120.
And the write window turns out to be the frame. A packed write requires R20
bit 11, buffer mode blanks the layer, and a DMAC-direct player holds the
window open for the whole data phase, so
dark fraction of a slot = record bytes / (DATA-PHASE rate x slot)
which is 1.0 at the container's own 582.0 KB/s: every frame delivered, on
time, pixel-exact, and none of them displayed. The rate in that expression is
the BURST rate, a third hardware number B1 has no test for. It reverses 61.5's
ranking -- a packed player that DMAs to RAM and paints with the measured 27.3%
blit is on screen 72.7% of every slot at any rate, and the two are equal only
at 2,131 KB/s = 3.7x the wire.
And a held channel costs the frame clock half its ticks without the clock
being able to tell: 487 of 1,038 V-DISP edges lost, zero late frames reported,
the player believing 12 fps while the screen ran at 6.37.
FINDINGS 64. ROADMAP K4 opened and fenced behind B2.
check.sh ALL GREEN before and after.
Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
prosolis