thejayman77
ec82764bef
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>
44 lines
2.0 KiB
Markdown
44 lines
2.0 KiB
Markdown
# rtl/gif_gs
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GIF path and Graphics Synthesizer logic. Matches `docs/contracts/gif_gs.md`.
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## Current contents
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- `gs_stub.sv` — GS shell with **two architecturally distinct write ports**
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(Ch75 namespace split):
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- `reg_wr_*` — privileged-block writes (16-bit offset within `0x12000000`).
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Latches `BGCOLOR` (offset `0x00E0`) into `bg_{r,g,b}`; other offsets emit
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`EV_MODE`.
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- `gif_reg_*` — GIF A+D register-number writes (8-bit reg# + 64-bit data).
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Decodes `PRIM=0x00`, `RGBAQ=0x01`, `XYZF2=0x04`, `XYZ2=0x05`,
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`FRAME_1=0x4C`, `ZBUF_1=0x4E` into per-register 64-bit latches; unknown
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reg numbers emit `EV_MODE`.
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- No VRAM, no drawing yet — that is the next architectural step.
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- `gif_path_stub.sv` — Wave 2 minimal GIF packet logger; project-local
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single-qword register-write format. Used by `tb_bgcolor_via_dma`.
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- `gif_packed_stub.sv` — real PS2 GIFtag parser (Ch72-Ch75). Handles PACKED
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(FLG=0), REGLIST (FLG=1), IMAGE (FLG=2), DISABLE (FLG=3). The
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`REAL_AD_REG_MAP` parameter selects the A+D dispatch port:
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- `REAL_AD_REG_MAP=0` (default, back-compat) — drives `gs_stub.reg_wr_*`
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using a project-local 16-bit offset carried in `in_data[79:64]`.
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- `REAL_AD_REG_MAP=1` — drives `gs_stub.gif_reg_*` using the real PS2
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8-bit reg# carried in `in_data[71:64]`. Source-of-truth: PCSX2
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`GSRegs.h`.
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## BGCOLOR reset value
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At reset, `bg_{r,g,b}` default to `0x40` each (mid-grey) rather than black.
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Rationale: this makes "gs_stub reset but no BGCOLOR write yet" visually
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distinct from "video output disabled / black frame" in Milestone A. Override
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is a `BGCOLOR` write from the test harness.
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## Pitfall: namespace conflation
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Ch74 conflated GIF A+D reg numbers with GS privileged-block offsets and
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mapped e.g. `0x14`→PMODE@`0x0000`. That is fiction — those are separate
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namespaces. Ch75 split them. **`ZBUF_1` is `0x4E`, not `0x4F` (that's
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`ZBUF_2`).** When adding a new GIF-context register, source the reg# from
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PCSX2 `GSRegs.h`, never from the privileged-block map.
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