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Pegasus
40 lines
2.3 KiB
Markdown
40 lines
2.3 KiB
Markdown
# GTE deadlines and deferred CPU work
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Pepsiman qualification10 first differs at return 1,514: source cycle
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856709465, native 856709463, one changed RAM page (1FF000). Both repeats
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produce identical RAM/CPU/log captures and later stop after 2,288 returns at
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a separate GPU scope guard. The original inputs are unchanged.
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Passive pre-fetch tracing is qualified against each untraced control. The
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first 96,369 PC/clock entries agree. The following entry is PC 8001E4B8:
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source 856413994, native 856413995. The preceding SWC2 reads the result of a
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DPCS command issued while prior load-wait credits still overlap CPU steps.
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Pending GPR-load values and kernel scratch registers are not assumed equal
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at this internal representation boundary.
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The runtime calculated its GTE stall from psx_cycle_count before publishing
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the instruction's pending base cycle. psx_advance_cycles then published that
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pending cycle and added the stale stall, counting the cycle twice. The same
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omission could arm a GTE command deadline too early or give an MFC2/CFC2 read
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the wrong load-overlap credit. The command latency itself is unchanged:
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original Octoshock 2.3 GTE_Instruction returns DPCS cost 8 minus 1.
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psx_gte_set, psx_gte_stall and psx_gte_read now publish pending batch and local
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charges before reading the clock. This is the same ownership rule already
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used by the multiply/divide deadline helpers. It applies to callers using
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the shared runtime, including interpreted and generated CPU paths.
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The BIOS/disc-free test_gte_deferred.c links the actual psx_cycles.c. Its
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short DPCS/ADDIU/SWC2 timing case fails before the fix. It then exercises all
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64 latency-table entries, prior command overlap, batch/local/both pending
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charges, elapsed/deadline boundaries, read credit and unchanged store credit.
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75,661 checks pass at O0 and O2. This fixture verifies shared timing helpers;
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full game replays and generated/interpretation coverage remain separate gates.
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Diagnosis receipts: pepsiman-boundary1514-cpu-comparison.json,
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pepsiman-source-boundary1514-11/passivity.json,
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pepsiman-native-boundary1514-12/passivity.json and
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gte-deferred-regression-01/{before,O0,O2}.log in the private accuracy campaign.
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No frame-specific clock offset, changed input, GTE arithmetic change, observer
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reduction or performance tuning is part of this correction.
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