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Comment by sam_goody | Hacker News Reader

Why would Amazon develop a custom Arm chip and not RISC-V?

Don't they have to pay a fee to Arm for this, even though it is being developed by them?

And would Google (which is allegedly developing their own Arm Chip) and Apple (which also has their own chip) not also benefit from backing Risc-V as well?

I have not been able to get clear in my head the relationship between Risc-V and Arm, and even more so exactly what responsibility down stream each user has.

Would appreciate the some ELI5 from knowledgeable HNers.

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Slightly related: is it more or less a given that eventually no one will use x64 chips (since Arm/Risc-V is more efficient)?

If not for servers, is it at least a given for desktop computers, as more software is written for ARM, and re-compilers like Rosseta improve?

If so, I know that Intel is investing in RISC-V, but has AMD given up the space entirely?

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Because by paying a fee to Arm, they get decades of architecture experience, support, peripherals (including a well-thought-out internal BUS), etc.

RISC-V has a good ISA, but there currently isn't a lot of silicon experience in the real world (relative to Arm and Intel, for example). And Amazon isn't going to roll their own to that degree. It's not worth the meager licensing costs.

It's like the difference between deploying Red Hat Enterprise Linux and Arch Linux. Each has it's place, but right now its advantages are in much different areas.

The most common use case is where ARM provide fully functional CPU core IP that you can put into your own SoC - in AWS Graviton's case that seems to be the ARM Neoverse line of cores.

You can also get architecture licenses where you can implement your own CPU core (from scratch, or by making tweaks to an ARM design) - Apple has one of these, but Apple is a special case in that they were one of the original partners when ARM was originally founded in 1990.

RISC-V on the other hand is an architecture that is open for anyone to implement, but the RISC-V foundation doesn't sell you a core design - you need to create your own, or find a partner to sell you one. It's also much newer, so there's less of an ecosystem around it compared to ARM.

> Don't they have to pay a fee to Arm for this

Because it's way cheaper than to do everything ARM provides on your own?

Gravitron3 is just using ARM Neoverse-V1 (which AFAIK are years ahead of any RISC-V cores). So they aren't different from Qualcomm/Ampere have been doing so far.

I think Ampere is planning to release a CPU with their own custom cores in the near future though. It's interesting whether Amazon will follow suite or not. It would be very bizarre if they tried switching to RISC-V in the near future though (I do find this semi -fanatical obsession with RISC-V a bit fascinating though but I don't think it's shared by many large corporations outside China..)

> Why would Amazon develop a custom Arm chip and not RISC-V?

The first Graviton was launched in 2018, which means it was in development and manufacturing even earlier. You couldn't build a high performance RISC-V chip back then. Even in 2023, RISC-V is significantly behind ARM/x86 in performance and software support isnt great either (for example, Debian has supported Arm for over a decade, but RISC-V support only arrived a few weeks ago).

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