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CPU Design: Fetch/Store vs. operating on memory (lemmy.zip)

submitted 7 months ago by [email protected] to c/[email protected]

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What are CPU designs which are not fetch/store but operate directly on RAM?

I only know about the design of the Nintendo Entertainment System (NES), where the CPU does not have registers (AFAIK) and operates directly on RAM, with fast access to low addresses in the RAM.

What CPUs/Systems do you know, which also do not do fetch/store for their operands? Which systems are out there? Why do CPUs like RISC/Arm/AMD64 use fetch/store, what are the tradeoffs? Are there different architectures for CPUs working on operands outside of fetch/store, DMA and stack machines?

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[–] [email protected] 2 points 7 months ago

Ah, I see what you mean now. Yeah I'm guessing there are code sequences where it's more efficient (either in clocks or code size or simple convenience) to operate on these 256 low addresses than repeating load/hit/store.