My REQ_DEPTH=1024 reduction was wrong: I sized it off a 478 peak from a SMALL
scene. The documented full-f52 replay peak is 6,115 (adjacent frame 3,610; even
2,048 clips) — ch439_timing_convergence_prefit.md. The raster cannot backpressure,
so an undersized FIFO SILENTLY DROPS Z-requests -> corrupt frame. The -0.074 fit
was on an invalid (drop-prone) config. Restore 8,192 as the correctness baseline.
The real timing fix is a registered/skid AR-handshake boundary (arbiter s2_arready
combinational -> texcache F_AR), NOT FIFO shrinking. Packaging that for Codex review.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The 8K request FIFO was 8x oversized (measured peak ~478; Codex's TB uses 1024).
Its read address routed to 8 spread M20K blocks -> 310MHz EMIF setup miss (-0.103,
MAX_FANOUT can't help: Quartus refuses to duplicate RAM-address regs, Warning 22471).
Shrinking to 1024 (2 blocks): 26.1 fit shows that path GONE, design clk +0.631->+5.693,
RAM 309/358 (86%) -> 277/358 (77%). New worst is a DIFFERENT, skew-dominated EMIF->
texcache-FSM path at -0.074 (TNS -2.032 -> -0.164).
SAFETY GATE before board load: confirm the full zsrt139f52 scene never bursts >1024
Z-requests in flight (peak I have is 478 from a smaller scene). Bump to 2048 if unsure.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The fog blend's tex_color*F multiply landed on the texture->color critical path
(u_texcache RAM -> u_tex|tex_color -> mult_126 -> raster_pixel_color_q, 46ns,
-6.165ns setup). Fog is a proven no-op for the current board scene (96.5% F=255),
so pay zero for it here.
FOG_ENABLE (default 1, byte-identical fog) added to gs_stub; each fog mux gated
(FOG_ENABLE && ras_fge) so FOG_ENABLE=0 constant-folds the entire fog cone away
(multiply, FOGCOL adders, s2_fog_f/persp_fog_f5 interp). Threaded through
top_psmct32_raster_demo_bram; set FOG_ENABLE(1'b0) on the active GS_SH3_LPDDR_FB
board arm (elsif at :1086, the one the QSF profile compiles). Fog stays default-on
everywhere else.
Verified: FOG_ENABLE=1 fog TBs unchanged PASS; FOG_ENABLE=0 (new tb_gs_fog_disabled
+ board scene TB) emits raw color = pre-fog datapath; board elaborates clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Two fixes for the failing STA (Codex-reviewed):
1. gs_texture_unit lerp8: remove the dead 0/255 clamp. For 8-bit taps and f in
0..15, a+floor((b-a)*f/16) is always in [0,255], so the clamp never fired -
but its comparators formed a 161-node combinational loop that failed
design-clock setup by 42 ps (tap[0][11] -> tex_cache_sel_q). Functionally
identical (tb_gs_texture_bilinear + texture TBs bit-identical PASS).
2. SDC: relax the u_zc_emit gray-code CDC max_skew 2.0 -> 2.5 ns. Post-fog
placement pushed actual skew to 2.010 ns (fails 2.0 by ~10 ps). Real ceiling
is the 3.225 ns EMIF period (one gray bit in flight); 2.5 clears the miss and
stays well under it. Documented relax of a conservative round number.
Acceptance (owner fit): no comb-loop warning, no tap->tex_cache_sel_q path,
all setup + max_skew slacks >= 0.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Per-vertex GS fog end-to-end (gs_stub emit incl. persp_emit5, gs_prim_list_feeder
XYZ2->XYZF2 on PRIM.FGE, gs_make_sh3_scheduler_fixture.py F/FGE packing), new fog
TBs, fidelity attribution tooling. Functional baseline before removing the dead
bilinear lerp8 clamps (Codex: 161-node comb loop -> -0.042ns setup fail).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
RTL (GS rasterizer, EE core stub, platform bridge, LPDDR4B path), sim regression
(272 TBs), docs, and tooling. Copyrighted PS2 content (BIOS, game code, GS dumps,
and all dump-derived textures/traces) is excluded via .gitignore and stays local.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
thejayman77