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Comment by snvzz | Hacker News Reader

>It's so hard to imagine so many years & a microarchitecture remaining so unchanging.

It's a shame, because it was the best design from ARM; they're now focusing on Cortex-A7x and Cortex-X, which aren't anywhere as power efficient[0].

Meanwhile, their revised Cortex-A57 has been surpassed in performance/power/area by several RISC-V microarchitectures, such as SiFive's U74[1], used in the VisionFive2 and Star64, or even the open source XuanTie C910[2][3].

0. https://youtu.be/s0ukXDnWlTY?t=790

1. https://www.sifive.com/cores/u74

2. https://xrvm.com/cpu-details?id=4056743610438262784

3. https://github.com/T-head-Semi/openc910

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I still use original Raspberry 2's (A53) in my server clusters, they are the lowest power devices that can saturate (good) SD cards on random writes/reads and still have performance left to serve calculations.

A72 in Raspberry 4 is really the pinnacle low power CPU performance if you count $ and compatibility (linux <-> GPU). ~3x can saturate symmetric 1Gb/s with advanced computation and still have calculations left.

You can buy neither, we'll see if the 4 ever comes back. The only thing I'm 100% of is that the 5 will have some drawback compared to both the 2 and the 4.

I can concur the peak of A55; the 5W TDP 22nm RK3566 in my RG353M is mind boggling! HL1 at 60 FPS and soon HL 2 at 30 FPS.

But Risc-V is not progressing with linux, mainly GPU drivers and integration is the problem. Historically the Chinese boards never got any attention and unfortunately you cannot depend on attention happening this time either.

Partly because now companies across the board(ers) are hiding kernel configs again. And "board support packages" are slow to be mainlined if ever.

Correction A7 is the R2 OG SoC, the last 32-bit only ARM!

If you have one hold on to it... I knew it was special!

They are removing 32-bit from modern ARM... but Intel will always have 32-bit!

Intel makes it sound like they will never drop their legacy support, and are just "testing the waters" with X86-S, but internally the discussion is over.

https://news.ycombinator.com/item?id=36013257

If anyone could give me a good answer to why 64-bit is useful I wouldn't argue.

But now I'm planning a 64-bit linux ARM distro that only runs 32-bit apps!

I'm reading between the lines a bit to try to answer, so if I missed your question or your intent please just point it out and I will adjust my answer.

32-bit is extremely useful. For intel, 16-bit is also very useful. The problem is that there is a strong divide between the people who find 32-bit and 16-bit useful at Intel, and the people who feel a need to force everyone onto UEFI "Class 3+" [1] and that everything else must be squeezed out, shamed, and moved to an emulator.

It sounds like Arm 32-bit support might be around for a while. I mainly wanted to clarify that Intel is dropping their 32-bit and 16-bit support.

[1] https://en.wikipedia.org/wiki/UEFI#Classes

32-bit Arm is not being removed. There's the modern 32-bit only Cortex-A32 "AArch32 for full backward compatibility with Arm v7" [1]. Also expect 32-bit code compatibility to exist for a long time on Arm embedded cores for code size reasons.

[1] https://developer.arm.com/Processors/Cortex-A32

It's being removed from the leading architectures.

Which is a very bold, and probably bad move.

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