PS2BUILD SDK Documentation

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Vector Units beta ​

New, hand-written section - see the note on the cheat sheet.

The EE has two attached Vector Units - VU0 and VU1 - small, specialized processors built for exactly the kind of math a 3D game needs a lot of: vector/matrix arithmetic, run in a tight loop, many times per frame.

Two units, two different relationships to the EE ​

VU0 sits close to the EE and can run in one of two modes: as a tightly-coupled macro/micro coprocessor the EE can issue instructions to almost like an extension of its own pipeline, or running its own independent microprogram. It's commonly used for per-vertex math the main CPU would otherwise have to do itself - skinning, lighting terms, that kind of per-object work - interleaved with regular EE code.

VU1 is more independent - it typically runs its own microprogram continuously, fed a stream of vertex/matrix data over DMA_CHANNEL_VIF1, and its most common job is exactly the one described in Graphics Synthesizer: transforming vertices and building the GIF packet that goes to the GS, so the EE doesn't have to do that packet-building work itself and can move on to the next frame's logic while VU1 keeps working.

No general-purpose "VU package" ​

Unlike, say, audio or networking, there's no single library in this SDK that wraps "the VUs" as a general facility - math3d (core) is EE-side vector/matrix math, not VU microcode. Real VU programs in this ecosystem show up as:

  • Hand-written VU assembly or VCL (a VU-targeting compiler) source, compiled separately and embedded/loaded like any other binary blob.
  • Pre-built microprograms bundled inside a higher-level library - gsKit/ps2gl each carry their own VU1 transform-and-build-packet microprogram as an implementation detail of "draw this," not something you write yourself unless you're replacing their pipeline.

If a project needs custom VU code (a bespoke particle system, a non-standard vertex pipeline), that's genuinely lower-level work than reaching for an existing package - closer to writing your own small piece of gsKit/ps2gl's job than consuming a library.

See also ​