Screenshot

A wireframe cube's 8 corners tumbling in 3D — with every rotation computed by the DSP-1 coprocessor (NEC µPD77C25), not the 65816. Each frame the CPU hands the DSP-1 a rotation matrix and 8 model-space points; the DSP-1 rotates them and hands back world-space coordinates, which are drawn as 8 sprites via orthographic projection.

This is the SDK's first DSP-1 example, and the third leg of the enhancement-chip family alongside SA-1 and Super FX.

SNES Concepts

DSP-1 command interface — the CPU drives the coprocessor over two registers (data + status) with an RQM handshake; see snes/dsp1.h
Offloaded 3D math — dsp1Attitude() builds a rotation matrix on the DSP, dsp1Objective() transforms each vertex through it, per frame
Orthographic projection — the rotated x'/y' map straight to screen; the DSP-1 does no rasterisation, so the CPU just places the 8 corner sprites
dsp1Init() — issues the $80 resync handshake so the chip starts in a known command-wait state

Firmware requirement

The DSP-1 runs Sony's mask-ROM firmware. Emulators that low-level-emulate the chip (including luna) need that firmware supplied — it is copyrighted and not shipped with the SDK:

# put your own dump here, then it persists
cp dsp1b.rom ~/.config/luna/firmware/dsp1b.rom
# or per-run:  luna run --dsp1-rom /path/to/dsp1b.rom dsp1_cube.sfc

Without it, the ROM still boots but the coprocessor stays inert (the cube won't move). High-level-emulation emulators (snes9x) run it firmware-free.

How to Build

cd examples/chips/dsp1_cube

make

Run dsp1_cube.sfc in an emulator with the DSP-1 firmware available.

Modules Used

console, dma, sprite, dsp1