[fierarul]

I don't understand the hype for RISC-V at all. It's an instruction set that would... just require a new backend for clang/gcc/Java and mean nothing to me unless somebody makes something that just obliterates a Ryzen.

Why should developers care? We barely have a decent ARM ecosystem after years of ARM routers and Raspberry Pi. Now we are supposed to be enthusiastic we will do that yet again for RISC-V?

Is it because it's somehow more open? But ARM wasn't that closed afaik - lost of folks produced it.

And Sun Microsystems open sourced a 64 thread CPU, the OpenSparc and nothing happened.

So, in a nutshell, why?

[socialdemocrat]

The approach of making a small instruction-set with optional extensions means RISC-V is very well suited for making specialized co-processors. This story discuss that more in detail: https://erik-engheim.medium.com/apple-m1-foreshadows-risc-v-...

On example of this is Esperanto Technologies, which has created an SoC with slightly more transistors than the M1, which has over 1000 RISC-V cores which implement the RISC-V vector instruction set extension to allow the processing of a large number of matrices and vectors. Basically the ET-SoC-1 as they call it is supposed to offer superior performance in the Machine Learning domain. 30-50x better performance with 100x less power consumption.

Esperanto Technologies are using the full flexibility of RISC-V by having more general purpose RISC-V cores, four of them, which are meant to run an operating system, which schedules machine learning tasks to this large number of smaller vector oriented RISC-V cores.

My understanding is that creating a good ISA is actually quite a task. RISC-V has over 1000 contributors over years who have made it happen. Esperanto Technologies apparently began with their own proprietary ISA for their coprocessors but found they could not beat RISC-V, and that making something better would just cost a lot more money and resources.

So in short the value proposition is in having a highly customizable ISA, that is well designed. There are no such other options on the market. ARM isn't highly customizable, since it has over 1000 instructions you must implement. RISC-V only has 47 instruction you must implement. All fairly simple ones.

[sifar]

>> There are no such other options on the market. ARM isn't highly customizable, since it has over 1000 instructions you must implement. RISC-V only has 47 instruction you must implement. All fairly simple ones.

I think this is a wrong comparison. There is a subtle difference here that is being missed.

CPU's become bloated over time as they get used differently, as the applications shift, as they try to address newer areas. And with each iteration, they still have to support the legacy code. That is how you end up with thousands of instructions

It is easy to have a lesser instruction count when you are starting from scratch and have no legacy.

What is going to stop RISC-V from becoming another ARM or perhaps x86 even, in another couple of decades ? When it spans such a large application space that most of the extensions become default and the core becomes bloated ? Time for another ISA then.

[jmwilson]

ARM licenses and royalties are not free. The royalties are a small but significant cost of a chip (1-2%) and licenses on the IP are a large R&D cost for the designer.

China is obviously interested in RISC-V as their access to the US market is threatened, and they could be a driver of wider use.

[miohtama]

India is also focusing on RISC-V, as they do not have their own chip industry yet. Depending on the Western countries for your processors is something any country wants to de-risk.

[fierarul]

This seems relevant if my corporation wants to put some $M into producing a thing. But I paid like $200 for my CPU and I would love a $500 Ryzen. Either way, I don't really care if 1% goes to royalties -- my price fluctuates more than that just because of our national currency.

[0xTJ]

I think that's the wrong question to ask. Aside from those writing kernels, compilers, JITs, etc., developers don't need to care, that's the point of programming languages and compilers. Throw a toolchain at a developer and tell them to do it and they can do it.

Comparing RISC-V to OpenSPARC is comparing apples to oranges. One is an ISA, the other is a hardware project.

What do you mean by "We barely have a decent ARM ecosystem". Are you talking about the tools to build for those processors? Or the tools to build new ones of those processors? Or the actual chips that are available?

I'm basically always within 10m of at least a half dozen ARM processors, and a handful of 8051s. At worst, RISC-V could be equivalent to ARM, without many of the parts that suck about it.

[fierarul]

Are we talking about RISC-V as an abstract idea, the same way we would talk about the benefits of functional or object oriented programming here?

Or is the end goal to have hardware in stores that people can buy?

Wasn't SPARC a RISC architecture? (Wikipedia says so, but I'm no expert).

> What do you mean by "We barely have a decent ARM ecosystem". Are you talking about the tools to build for those processors? Or the tools to build new ones of those processors? Or the actual chips that are available?

I remember the early OpenWRT / RPi days when many packages weren't even compiling for ARM. Now I think we are in a much better shape. The chips were available, but the software ecosystem was way behind.

> At worst, RISC-V could be equivalent to ARM, without many of the parts that suck about it.

What I do know about ARM sucking is that the whole board design makes each product need a customer kernel more or less. Which is why we still don't have a "Linux for your phones". What I've read about RISC is that it's going to be roughly the same: encourage a lot of co-processors which mean custom boards to me and probably custom kernels.

[nickik]

Because you can't make an open ARM or x86 core. Yes SPARC was open before and not much happened from it, but just because something didn't work the first time, doesn't mean it not a good idea. The world is different now compared to then.

If we ever want to live in a world where we have open implementation that have a huge software ecosystem that is ready, we need an open well support ecosystem.

So, if you don't care about open source, then you don't care about RISC-V. If you do however, you probably should care.