Comment by themafia

1 month ago

Awful compared to what?

I've seen benchmarks that go both ways in terms of a "winner" but in terms of overall variance there seems to be very little. There are some cases where ARM64 or RISCV do better and there are some cases where x86_64 does better. I can't see code density being a relevant factor when picking one ISA over another.

We've got good compilers now anyways.. outside of power consumption.. the ISA wars are dead.

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themafia

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bell-cot  1 month ago

Technically, code density still matters - because both L1 cache memory and L1 instruction fetch misses are very expensive.

But as you point out, code density gets far less attention in tech circles these days. And higher-level decision makers rightfully focus on higher-level system performance metrics.

adgjlsfhk1  1 month ago

> outside of power consumption.

This is a pretty huge caveat. >90% of cpus are <1W (usb cables, wifi cards, storage controllers etc), and 99% are <10W (phones, lots of laptops)

  • adrian_b  1 month ago

    You are right about the order of magnitude of the percentages, but the CPUs <10 W are in phones, tablets, small SBCs (single-board computers) and only in a small fraction of laptops and mini-PCs.

    The vast majority of laptops and mini-PCs uses more powerful CPUs. While 15 W CPUs were normal many years ago, when Intel launched the "Ultrabook" campaign, in recent years, due to better cooling, most laptops and mini-PCs use 25 W to 30 W CPUs, and a significant fraction of them (bigger than the fraction of the laptops/mini-PCs that uses <=10 W CPUs) uses CPUs with a TDP between 35 W and 65 W.

    • adgjlsfhk1  1 month ago

      Lots of laptops have ~30W cpus, but that's peak usage. A typical laptop has a ~50WH battery, and a ~5W screen. If it's getting 5hr battery life, that means the CPU is averaging <5W.

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