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https://github.com/RetroPortingToolKit/psxrecomp
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Alex Vanderveen
493055846d
THE BUG, measured end to end. Legend of Mana's land-creation effect renders as hard-edged full-screen wedges because ONE sector of a multi-sector scene load never arrives: cd_read_log shows LBA 125111 -> 0x0E1F18 followed by LBA 125113 -> 0x0E2718 -- destinations one sector apart, LBAs two apart. Sector 125112, which the ISO shows holds the effect's 5-colour per-vertex palette (0x0888F8 = (248,136,8), 0xB0F8F8 = (248,248,176)), was skipped; sector 125113's raw file bytes landed at its address and were faithfully rendered as 216 distinct vertex colours. DuckStation places 125112 correctly and draws the clean bloom. The skip is manufactured by accelerated pacing. At authentic cadence the guest has a full sector period (~6.6 ms at 2x) to ack each data-ready INT1; the one-deep pend-then-lose below is Beetle-faithful, and a loss there means the game truly was too slow. With the speed divisor or bounded-instant mode active, sectors arrive in a fraction of that period, so a guest that is merely BUSY -- here, mid scene-load decompression -- gets a sector clobbered that hardware would have delivered. s_int1_lost counted it; the stream corrupted silently. Fix, class-level per RULE -1: when running FASTER than hardware, never overwrite a sector the guest has not consumed -- hold delivery, capped at the authentic sector period, then fall through to faithful clobber semantics. Accelerated mode is thus never slower than hardware and never lossier than hardware; loads stay near-instant while the guest keeps up and degrade toward guest speed when it does not. XA/streaming modes are excluded by the same gates as apply_read_speed and keep authentic timing. Warm routes keep their existing indefinite handshake. New counters accel_consumer_waits/_wait_cycles in cdrom_state: nonzero is healthy (the enhancement waited); int1_lost rising while the divisor != 1 is the regression tripwire. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>