# FPGA Prior Art (Adjacent Consoles)

Codex correctly noted that no credible open-source HDL PS2 core surfaced. What
*did* surface, and what Codex did not log, is a small cluster of PSX-on-FPGA
projects. None are PS2, but they are the closest real-world templates for how
a console-generation FPGA effort is scoped, built, and validated.

## PSX_MiSTer — Robert Peip (FPGAzumSpass)

- Repo: https://github.com/MiSTer-devel/PSX_MiSTer
- Most feature-complete and widely-used PSX FPGA core.
- Author's prior work: GBA, Atari Lynx, WonderSwan cores on MiSTer.

The methodology is the useful part, not the RTL:

1. Peip wrote his own cycle-accurate PSX *software* emulator first.
2. Only then did he start the FPGA implementation, using the emulator as a
   continuous cycle-level golden model.
3. Test vectors and traces were generated by the emulator and replayed into
   the RTL under simulation.

Why this matters for retroDE_ps2:

- This is the only known methodology that has produced a credible, accurate
  console-gen FPGA core from open-source work. Worth taking seriously as a
  starting playbook, even if the final plan diverges.
- It implies the reference-emulator choice (PCSX2 vs DobieStation vs Play! vs
  a purpose-built tiny one) is an architectural decision, not just a
  debugging nicety.

## PS-FPGA

- Repo: https://github.com/PS-FPGA/ps-fpga
- Separate PSX-on-FPGA effort. Useful as a comparison point for project
  organization, module decomposition, and test harness layout.

## pgate1/PlayStation_on_FPGA

- Repo: https://github.com/pgate1/PlayStation_on_FPGA
- Smaller / more hobbyist-scale PSX FPGA. Useful as a "minimum viable scaffold"
  reference if the project needs a leaner starting shape than PSX_MiSTer.

## What these do not give us

- Zero usable RTL for EE, GS, VU0/VU1, VIF, GIF, SPU2, or the DMAC. The PSX's
  GPU is not a GS, its CPU is not an R5900, and it has no VU complex. Nothing
  transfers as a datapath.
- No GIF/GS packet path equivalent. This is a PS2-specific problem the PSX
  cores did not need to solve.

## What they do give us

- A methodology template: golden-reference emulator → RTL with cycle-level
  trace comparison.
- A feel for scope discipline: PSX took Peip years *with* strong prior FPGA
  experience. PS2 is materially larger.
- Practical file layout, build, testbench, and host-integration patterns on
  MiSTer-class platforms.

## Planning implication

Before Phase 0 lock, it is worth deciding explicitly whether retroDE_ps2 will
follow the "cycle-accurate reference emulator first" pattern, adopt an
existing emulator (PCSX2 or DobieStation) as the golden model, or take a
different validation approach entirely. The answer changes Phase 1 scope.
