[dmbaggett]

Yes, for Crash Bandicoot we had to entirely skip the C SDK for everything performance-critical; pushing arguments onto the stack and the SDK popping them off for each function call used more cycles than the underlying operation in many of these SDK calls.

Sony explicitly forbade this, presumably because they envisioned the API established by the C SDK as a way to ensure future backward-compatibility. We just ignored the rules and hoped the superior performance we could achieve would overcome any bureaucratic obstacles.

We also had to reverse engineer some of the PS1’s really nice capabilities. I only learned the hardware supported vector pipelining for strip rendering by noticing the coordinate values move from one register set to the next in the debugger.

Seeing that was a revelation: when rendering a polygonal mesh, you naively have to project three coordinates for each triangle. But if you convert your mesh into sequences of polygonal strips where each triangle shares an edge with the next triangle in the mesh, you only need to project a single additional vertex for each additional polygon in the strip. Observing the behavior in the debugger, it was obvious to me that the Sony hardware had in fact been optimized for this approach. But not only were we not given any documentation on this, we were instead told to use the C SDK, which didn’t expose this capability at all.

The PS1 also had 2KB of “scratchpad” that was slower than registers but much faster than RAM. Hearsay was this was a way for the CPU designers to make use of the physical space on the die meant for floating point instructions which the MIPS CPU in the PS1 didn’t have.

I used the scratchpad to store projected 2D “stamps” of the 3D world (stored in an octree) and Crash: a kind of low-res Crash Flatland. I could then check for X/Y collisions between Crash and the world very rapidly by inspecting the flatland bitmap stored in the 2K scratchpad. This was Mark Cerny’s idea; he was our producer on the Crash games and has also been responsible for PS2 through PS5 hardware.

[znpy]

Hey I just wanted to chime in and say that I spent a lot of time in my infancy/youth playing crash bandicoot, thank you very much.

Also, i’ve seen many videos on YouTube about all the crazy things you had to do to make stuff work. And every time i get to read some additional detail it’s always super intriguing…

Have you considered doing something like a documentary? Like, a series of long form videos on the topic? With interviews to people involved etc?

[dmbaggett]

Hopefully you’ve read the Polygon article and seen the videos with Andy Gavin talking about the underlying tech. I was going to do part two of the video series but COVID killed it. Maybe we’ll revive that; it would be fun.

[gryson]

Thank you for posting this!