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I'm trying to figure out why this cart only runs at 10 FPS on a Raspberry Pi Zero. stat(1) returns 0.49 and stat(7) returns 30. However, the screen is only updating at 10-11 FPS. Other carts with higher stat(1) values don't show this problem, so it seems specific to something in this cart.

I can optimize to get the CPU usage down to 17%, and then the real framerate becomes acceptable. However, I'd actually like to understand why it is slow so I can work around it. (Also, I'd prefer to be able to use the whole CPU budget instead of just 17% of it!)

I assume what's happening is that the pico-8 CPU costs are optimistic for some instructions, and the actual cost on the Pi Zero hardware is higher. But which instructions?

Are there specific instructions I should be avoiding?

Are there specific types of drawing (like large map areas, or off-screen drawing) I should avoid?

Can I hook up a profiler to see what it is spending its time on?

The original raspberry pi post (https://www.lexaloffle.com/bbs/?tid=3085) says math-heavy carts run slowly. Is that still true?

Are there any performance tricks for writing carts that run well on a raspberry pi?

Cart #slow-0 | 2020-06-29 | Code ▽ | Embed ▽ | No License

P#78645 2020-06-29 00:59

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