Files

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thejayman77 2e2c1e9ca6 Ch443e: binomial 4th line buffer + prefetch lead-2 (fix lookahead underflow)

The Ch443d board per-frame diagnostic identified the real displayed-frame
failure as a BINOMIAL vertical-lookahead starvation: displaying source
row r while interpolating r-1/r/r+1, the prefetch led by only one row
(next_fetch <= disp_row+1), so the lookahead row r+1 was still in flight
when the 3x3 filter read it (board: scan_y=33, nf_v=34, cause_lookahead=1,
read-error=0, deterministic every frame).

Fix (BINOMIAL_3X3_FILTER only; legacy 2/3-buffer, lead-1 paths unchanged):
- Add a 4th rotating line buffer (lb3) with its own RAM-local write/read/
  cache registers. The 3x3 filter needs r-1/r/r+1 resident (3 buffers), so
  leading by 2 (fetch r+2 while displaying r) without overwriting r-1
  requires a 4th buffer.
- Prefetch lead-2 for binomial: disp_row_limit_e = disp_row+2. The in-flight
  r+2 lands in the 4th buffer (b+2 mod 4), always distinct from prev/cur/next
  (b-1/b/b+1 mod 4), so it never clobbers a row being read.
- Modulo-4 rotation everywhere: V_SOURCE_BUF%4, stretch_buf_q, next_fetch_buf,
  reset alignment at V_SOURCE_START, and the read-cache prev/cur/next case
  extended to 4 branches with (b-1)/b/(b+1) mod 4 selection + first/last-row
  clamps preserved.

New tb_gs_scanout_binomial_lookahead reproduces the board condition under
realistic EMIF latency (LAT=7) + backpressure and proves: NO binomial
lookahead underflow, correct 3x3 output across modulo-4 wrap + clamps (full
oracle, 1280 px), and coverage that mid-frame rows past V_SOURCE_START+1
with vphase!=0 were exercised under prefetch pressure.

All green: binomial (4-buffer, identical output), lookahead (new),
scanout_lb {,_hstretch,_psm32_256,_fb}, scanout_restart, scanout_diag,
ps2_hps_bridge, and the complete f52 replay BYTE-IDENTICAL (Z 0/307200,
COLOR 0/245760). Also commits the Ch443d board evidence that identified
this defect. No Quartus/board/push from here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-07-23 15:24:37 -04:00

clut_loader_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

clut_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

ee_gs_priv_bridge_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gif_image_xfer_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gif_packed_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gif_path_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_alpha_blend.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_async_fifo.sv

Ch440 review fixes: 93-bit per-bank test coverage + soften M20K claims [READY FOR REVIEW]

2026-07-21 10:28:31 -04:00

gs_axi_aw_regbuf.sv

Ch443: combined timing repair for both Ch442 setup families

2026-07-22 11:19:09 -04:00

gs_axi_r_regbuf.sv

Ch443d: registered AXI R buffer (texcache fill) + drop fill_data_q reset

2026-07-23 10:03:01 -04:00

gs_axi_w_regbuf.sv

Ch441: one-entry fully-registered W buffer, Z-RMW master -> wr_arb s2 [READY FOR REVIEW]

2026-07-21 14:12:11 -04:00

gs_grad_divider.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_lpddr_axi_master.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_color_blend.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_fb_writer.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_lpddr_map_pkg.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_rd_arb.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_rd_probe.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_scanout_lb.sv

Ch443e: binomial 4th line buffer + prefetch lead-2 (fix lookahead underflow)

2026-07-23 15:24:37 -04:00

gs_lpddr_scanout.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_lpddr_wr_arb.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_wr_probe.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_lpddr_z_rmw.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_lpddr_zc_emit.sv

Ch443: combined timing repair for both Ch442 setup families

2026-07-22 11:19:09 -04:00

gs_pcrtc_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_persp_uv.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_prim_list_feeder.sv

Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

2026-07-20 19:56:46 -04:00

gs_reciprocal_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_stub.sv

Add FOG_ENABLE param, prune fog cone on the board profile (fix -6.165ns setup)

2026-07-20 21:31:14 -04:00

gs_swizzle_psmct16_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_swizzle_psmct32_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_swizzle_psmt4_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_swizzle_psmt8_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_texel_addr.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_texture_cache.sv

Ch443d: registered AXI R buffer (texcache fill) + drop fill_data_q reset

2026-07-23 10:03:01 -04:00

gs_texture_unit.sv

Fix signoff timing: remove dead bilinear clamp (comb loop) + relax gray skew 2.0->2.5ns

2026-07-20 20:03:42 -04:00

gs_tile_ram.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_tile_reload.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

gs_z_flush_writer.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

README.md

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

vram_bram_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

vram_normalize_pkg.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

vram_stub.sv

Initial commit: retroDE_ps2 — first-of-its-kind PS2 GS FPGA core (DE25-Nano / Agilex 5)

2026-06-29 20:10:50 -04:00

README.md

rtl/gif_gs

GIF path and Graphics Synthesizer logic. Matches docs/contracts/gif_gs.md.

Current contents

gs_stub.sv — GS shell with two architecturally distinct write ports (Ch75 namespace split):
- reg_wr_* — privileged-block writes (16-bit offset within 0x12000000). Latches BGCOLOR (offset 0x00E0) into bg_{r,g,b}; other offsets emit EV_MODE.
- gif_reg_* — GIF A+D register-number writes (8-bit reg# + 64-bit data). Decodes PRIM=0x00, RGBAQ=0x01, XYZF2=0x04, XYZ2=0x05, FRAME_1=0x4C, ZBUF_1=0x4E into per-register 64-bit latches; unknown reg numbers emit EV_MODE.
- No VRAM, no drawing yet — that is the next architectural step.
gif_path_stub.sv — Wave 2 minimal GIF packet logger; project-local single-qword register-write format. Used by tb_bgcolor_via_dma.
gif_packed_stub.sv — real PS2 GIFtag parser (Ch72-Ch75). Handles PACKED (FLG=0), REGLIST (FLG=1), IMAGE (FLG=2), DISABLE (FLG=3). The REAL_AD_REG_MAP parameter selects the A+D dispatch port:
- REAL_AD_REG_MAP=0 (default, back-compat) — drives gs_stub.reg_wr_* using a project-local 16-bit offset carried in in_data[79:64].
- REAL_AD_REG_MAP=1 — drives gs_stub.gif_reg_* using the real PS2 8-bit reg# carried in in_data[71:64]. Source-of-truth: PCSX2 GSRegs.h.

BGCOLOR reset value

At reset, bg_{r,g,b} default to 0x40 each (mid-grey) rather than black. Rationale: this makes "gs_stub reset but no BGCOLOR write yet" visually distinct from "video output disabled / black frame" in Milestone A. Override is a BGCOLOR write from the test harness.

Pitfall: namespace conflation

Ch74 conflated GIF A+D reg numbers with GS privileged-block offsets and mapped e.g. 0x14→PMODE@0x0000. That is fiction — those are separate namespaces. Ch75 split them. ZBUF_1 is 0x4E, not 0x4F (that's ZBUF_2). When adding a new GIF-context register, source the reg# from PCSX2 GSRegs.h, never from the privileged-block map.