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Comment by snvzz | Hacker News Reader

The real reason RISC-V is succeeding, relative to ARM:

If you make your own CPU

- With ARM, You have to pay ARM for ISA license (after a several months long negotiation), and you cannot license your CPU design to anyone, as ARM has the exclusive right to do that with their designs.

- With RISC-V, you get a free ISA license, and you can license your CPU design to others.

If you do not make your own CPU

- With ARM, you can (after a several months long negotiation) license one of the few designs ARM has available. There's no other vendors that can offer you ARM CPU designs.

- With RISC-V, right now, you can license any among hundreds of options available, from tens of vendors. The licensing process is usually very short and straightforward. Alternatively, there are some open hardware designs. You can get commercial support for some of them.

Frankly, unless ARM does radically change their business model, I do not expect them to survive.

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> Frankly, unless ARM does radically change their business model, I do not expect them to survive.

Survive what? I don't see RISC-V disrupting much of ARM's bigger-named business (eg, phones, with some inroads into other things like Apple Silicon & laptops). Maybe Amazon pivots into RISC-V for the next Graviton? But that also seems unlikely unless someone with very deep pockets invests in making an actually competitive RISC-V CPU core at the mid/high end.

ARM's low-end market seems likely to be taken over by RISC-V. So like the Cortex M series days seem numbered without a change in the business model. But that seems like about it.

> Survive what? I don't see RISC-V disrupting much of ARM's bigger-named business (eg, phones, with some inroads into other things like Apple Silicon & laptops).

Go back a decade or so: how many people thought that ARM could compete against Intel/AMD?

One decade ago was 2012.

Chromebooks on ARM have already been out for a year. Windows RT for ARM was coming out later in the year. Smart phones are clearly all going ARM. The 64 bit ARM spec was out and people were excited about it.

I think it was a lot clearer that ARM was going to succeed x86, as compared to looking forwards now as to where RISCV will beat ARM.

I do suspect the microcontroller ecosystem will have lots of RISC-V. But it seems a lot less clear that it will succeed ARM in the mobile/laptop/desktop/server markets. I personally do not think that’ll likely happen any time soon.

The microcontroller space is where the cost of the ISA really matters, too. Most of the other IP in a microcontroller is cheap. If you compare that to a mobile SoC, the CPU core often isn't even the most expensive block.

ARM still isn't really competing against Intel/AMD. It took an entirely new form factory that radically changed the consumer landscape for ARM to get a foothold at all. What is RISC-V's smartphone explosion?

ARM has so far, outside of Apple and very limited cloud experiements (and some very badly received laptop experiments), not really put a dent in Intel/AMD's markets. But all of this was fueled by the once-in-a-generation explosion that gave ARM untold increases in adoption "for free". RISC-V has seemingly nothing similar, and RISC-V itself certainly isn't manufacturing any such radical shift.

Graviton2 is generally available and depending on your codebase and dependencies can be a drop-in replacement. I was amazed at the breadth of ARM docker images that exist for common use cases.

Umm, ARM has the share in the phone market where Intel/ AMD couldn't make a dent...

It's a matter of time other shares will be eaten when x86 is having hard time innovating over its decades old design.

More battery time for consumers laptop and less electricity bill for cloud vendors are something very attractive.

> Umm, ARM has the share in the phone market where Intel/ AMD couldn't make a dent...

Yes, obviously, which I mentioned repeatedly. For ARM to be successful outside of embedded it took an entirely new category of device to appear. What's RISC-V's entirely new category of device where it happens to be uniquely positioned?

> It's a matter of time other shares will be eaten when x86 is having hard time innovating over its decades old design.

Based off of what? The only ARM CPU that isn't thoroughly outclassed by AMD & Intel's x86 CPUs is Apple's, and Apple sure isn't licensing that to anyone. And so far every time ARM has tried to enter the domain of x86 it's been either absolutely embarrassingly bad (laptops) or mediocre at best and only for the very latest generation at that (servers)

> less electricity bill for cloud vendors

ARM server CPUs have the ~same 250W TDPs of Intel & AMD server CPUs. There's no power savings to be had here.

>Go back a decade or so: how many people thought that ARM could compete against Intel/AMD?

Hello, that would be me? :)

A decade ago was 2011 / 2012. Not a lot ( if not zero ). Even Anand from Anandtech was still cheering on Intel because of Intel's foundry leadership.

Wrote it on Anandtech and AppleInsider ( probably on HN with my old account as well ) the moment Intel decide not to make chips for iPhone or Fab Chips for iPhone in 2011. That was before Intel announced their Customer Foundry. They later went to do a JV with a Chinese company which later become Spreadtrum now known as Unisoc.

The whole reason why Arm competed against Intel and AMD wasn't because of ARM the ISA. It was the business interest and Foundry model. On a projected annual 1.5B Smartphone shipment by 2020 ( Which turns out to be a little too optimistic ), and 150M PC shipment by 2020 and continue to trend downwards. ( A little too pessimistic ) Even had TSMC not taken over the leading edge crown or stayed one node behind Intel the market today would still have been the same. The smartphone market was far bigger than the PC. This actually ties to why people were dismissing moore's law in the late 00s and early 10s. And it was the economy scales that wins.

What turns out to be wrong though was Tablet didn't take over PC. We are not in a Post-PC world. E-Sport (x86) picks up and PC as a Gaming platform is bigger than anyone could imagine. PS4 would move to x86 ( I dont think rumours of PS4 on AMD x86 even began til early 2012, and only partly confirmed by 2013 ) GPU is no longer a Gaming niche but a fundamental in Data Science. The hype of so called Cloud where everyone laughed at or sceptical of ( that is including me ) turns out to be multiple order of magnitude bigger as well. x86 ( Intel / AMD ) thrives because of that.

I worked in the CPU business 30 years ago and it was clear then that ARM would be very competitive. I was in the UK. Perhaps that made a difference.

RISC-V is more than a decade old.

A decade ago Microsoft was releasing ARM based laptops (or laptop like tablets if you insist). They were slow as hell Tegra 3 disappointments, but it was happening 10 years ago.

Their phone business is probably safe for now, but as you said they are set to lose a lot of their embedded business. The stuff that powers your HDD, your fridge, your IoT devices. Lots of high volume use cases

IDK about Cortex M being soon overtaken by RISCV.

There is a huge discussion about peripherals and IP. You can buy peripherals for ARM all day long, they’ll work from one chip to another for the most part. Once everyone can “make their own CPU”, expect fragmentation in the peripheral interfaces.

I think low end cortex A and R are where V will shine first. Something like a CISCO IP phone, not an iPhone.

> ARM's low-end market seems likely to be taken over by RISC-V. So like the Cortex M series days seem numbered without a change in the business model. But that seems like about it.

Doesn't that inevitably set up a classic Innovator's Dilemma?

I don't think so. ARM may just not care about losing that market. The CPUs they design at that ultra-low-end really don't carry over into the mid & high ends, which is where the high profile design wins & "high" (relatively) margins are anyway. Like what makes for a good hard drive controller doesn't really have anything at all to do with what makes a good smartphone CPU. So RISC-V winning at hard drive controllers or other (tiny) embedded usages is not really setting up an "S" curve for explosion here to challenge ARM's markets. They are really fundamentally different markets & products.

Kinda like how Intel just never cared about going after embedded, and they're not exactly struggling as a result of that. With the big asterisk of smartphones where scaling up proved a quicker path to shipping than scaling down, at which point inertia took over, but for that to repeat would require a currently unknown new product category.

I'd bet on AR glasses that somehow need to squeeze the compute power of a midrange cellphone into the form factor of a pair of glasses.

And if ARM started allowing everyone to use their IP for free you would expect them to survive? ARM the architecture might survive but probably no ARM the company. IMHO a more likely outcome with Risc (assuming it gets widely adopted) would be one or two companies like Samsung, Qualcomm, AMD or even Intel gaining a massive advantage and profiting from it instead of cheaply licensing their designs to other companies. I don’t really see how is that preferable to the ARM model where company can theoretically license the most advanced ARM cores there are (of course aside of what Apple is doing) or mostly equal terms.

Of course RISC might push them to make their licensing mechanism to be more flexible if they start considering RISC an a real threat to them (I don’t think this is very likely to happen in the near future, though)

>if they start considering RISC an a real threat to them

I'm afraid they have seen RISC-V as a threat for a while now. It has already been years since their first FUD campaign.

>if ARM started allowing everyone to use their IP for free you would expect them to survive?

That's not how I see ARM surviving.

One way ARM could survive is by doing what the MIPS owners did: Abandon the ISA, move to RISC-V, use your extensive expertise to make competitive cores, and your clout in the market to sell them to your pre-existing clients.

They could totally pull it off, but it would honestly surprise me if they did so, considering how poorly they've dealt with RISC-V so far.

> The way ARM could survive is by doing what the MIPS owners did: Abandon the ISA, move to RISC-V, use your extensive expertise to make competitive cores, and your clout in the market to sell them to your pre-existing clients.

Even if that’s their best bet, long term, I don’t see why they would have to start doing that right now. Why would they leave their castle with its golden egg-laying goose, only because they know it won’t live for X more years?

Timing such transitions is always difficult (you can’t wait until your goose is dead), but I think they’re better of waiting at least a few more years.

The MIPS owners were in a different situation, weren’t they? Their goose already was dying or even dead.

ARM has extensive IP and know how. They could build up and sell high performance RISC-V IP/cores now and prevent RISC-V focused companies like SiFive from gaining a foothold by denying them revenue and investment.

Alas, that would probably have worked better 2+ years ago, there is a lot of movement now.

It seems like Intel has realized this. They tried to buy Sifive, but have now themselves joined as a major RiscV International sponsor and are investing heavily in the ecosystem.

Of course there is a downside there too, because it accelerates a software and hardware ecosystem transition to a different architecture that can enable other players. We'll see how it plays out

> Intel has realized this

One of the reasons Intel is spending money on RISC-V could be that they want to undercut Arm, as the latter are now beginning to be competitive in Intel's X86 world. RISC-V is going to succeed at all as an ISA, it is going to hurt Arm before Intel.

intel bought into arm as well, then sold it off like many other things in the past. it will be interesting to see if intel is forward-thinking this time, or just chasing profit ... again.

>I don’t see why they would have to start doing that right now.

Me neither, but spreading FUD about RISC-V as they've been doing doesn't help their credibility should they take the MIPS path.

That's just a job for the marketing department. I can hear them already:

ARM's vast experience brings the quality you've come to expect to the RISC-V world. Want to lower TCO and level up your designs, while leveraging existing experience, but worried about low quality IP polluting your tech? Fear not. etc...

You can probably let an AI spew this stuff by now. Training data is easy to find.

> Training data is easy to find.

Got a good chuckle from that, I did! :D

Take a look at the Halloween Documents and then look at Windows Subsystem for Linux. This industry can absolutely forgive FUD in the long term if a company changes its path.

Long term, yes.

But is RISC-V somehow superior to ARM soo much that ditching their ISA and switching to RISC-V is their only way to survive. Is there anything specific about RISC-V that would ARM to make significantly more efficient cores (and I don’t think that there is any evidence that this would be the case). Because if not it would an exceptionally bad move for ARM to do (basically like Intel deciding to ditch AMT64 to make ARM or Risc cpus.

Abandoning the ISA is probably too extreme.

MIPS was pretty dead when they abandoned it, ARM is still alive and well.

ARM could survive by making the ISA free and competing by having the best ARM core designers and designs, and/or by having proprietary addons for media handling/decoding.

They will have no choice. Either ARM becomes irrelevant as people switch to an easier to license ISA, or they have to swallow a different profit model and compete by having the _best_ ARM cores in an open market of ARM IP.

The trend with RISC-V suggests that ISAs are going to be commoditized and the real value will be in the implementations themselves.

> real value will be in the implementations themselves.

It is not that difficult to re-target a micro-architecture (what you call implementation) to a new ISA, especially if the ISAs relatively close, as most modern ISAs are. RISC-V and Arm ISAs are an example where that should be especially easy.

Totally, all the more reason that the specific ISA is less important than the implementation/micro-arch.

Why pay for ARM if you can retarget to RISC-V and still retain most of the benefits of your designs.

As "baq" also says: you pay Arm (or Apple, or Qualcomm or ...) for the micro-architecture. I expect Arm to drop licensing costs for their ISA to zero to compete with RISC-V at the low end.

Right now, the Arm ISA has much better micro-architectures than RISC-V, why bother with RISC-V? I think this will change over the next 5 years. One of the ways to change this could be Arm selling RISC-V implementations.

Of course there are also dangers in RISC-V: one is that we will get too many RISC-V versions, so no stable software ecosystem emerges for any single one of them. Adapting Linux, GCC and so on to your specific version of RISC-V (or any processor really) is rather expensive.

you'll pay ARM for a good ARM RISC-V CPU.

Market segmentation exists. RISC-V being open means it's also open to ARM. You may, in the future, pay ARM to license a SoC that's a RISC-V ISA core or four with their tried-and-true peripheral cores and maybe a couple of M0 cores to boot.

Assumes that Arm have no implementation IP - which comes with the ISA and is not available to others - and that the only factor in choosing an ISA is how 'easy' it is to license. Very strongly disagree with these assumptions.

> Very strongly disagree with these assumptions.

It is the fundamental basic business ideas that they have it all wrong. Which is why every time these discussions came up they are non-productive. It is no different to saying Linux would take over desktop in the 90s because it is free. We are in 20s and coming up 30s. It is still not happening.

But at least ( or hopefully ) we have passed stage where RISC-V is fundamentally better ISA than ARM. And talk about the business aspect of it.

Edit: Ok I was wrong, the ISA debate is near the bottom of the page. I didn't invent the term "Riscy Silver Bullet" for no reason :).

> It is no different to saying Linux would take over desktop in the 90s because it is free. We are in 20s and coming up 30s. It is still not happening.

The desktop? Maybe not. But Linux has done well with laptops in recent years (Chromebooks). Definitely not "taken over", but 30 million units a year is nothing to sneeze at either.

ChromeOS is Linux in name only, just like Android. Google just needed a kernel and a functional low level stack. They can switch to Fuchsia in the near/medium future and most user would probably not notice a thing.

"Riscy Silver Bullet" is very good.

Completely agree.

ARM won't become irrelevant as long as Apple exists.

Arm is the fourth ISA for the Macintosh and its descendents. Apple has shown three times that they're anything but wed to architectures.

"And if ARM started allowing everyone to use their IP for free you would expect them to survive?"

Irrelevant question that no one anywhere has any obligation to care about.

Well the comment above (which I assume you didn’t read) implied that ARM would have to changes it’s business practices to remain competitive. Whereas I think it’s current businesses model is the main reason it’s still competitive.

Longterm I’m afraid that a completely open ISA might result in a less competitive market as long the cost of developing competitive cores is high enough. All top players could just start behaving like Apple and just keep their cpus for their own products/cloud services instead of selling them at commodity prices and losing a competitive advantage. So having a ‘neutral’ player like ARM might still be preferable.

I don't think the parent comment was suggesting we have an obligation to care about ARM's survival.

But ARM probably cares about ARM's survival so it is relevant to the discussion about what future decisions ARM might make.

When the landscape changes that some business model depended on, it is no one else's obligation to care if some business using that model adapts or doesn't.

I literally quoted a question that asks "you expect", and what I am pointing out, not declaring but observing, it's already a fact regardless if I say it, that neither you or I nor anyone else has any obligation to expect anything.

It doesn't even matter if we do expect something. Even if you were some kind of Arm fan like being a fan of a sneaker brand or a celebrity, your good wishes still don't change anything.

"you expect" is just irrelevant in this question. Arm can adapt to the new environment or not. The environment is changing and it doesn't matter if anyone likes it or not.

And the nature of the change, people giving away something that someone else used to be able to charge rent for, is not unfair or unethical or immoral in anyway, nor is it any kind of net loss for society as a whole, so there is no argument for doing something to artificially protect Arm's business model.

Steve used to sell cakes. Sally gave everyone her recipe for cake and now fewer people buy Steve's cakes. So what?

Do you mean to say that Sally should not be able to give away her own cake recipe? Steve doesn't like it because he had a good gig going for a while there, but so what? The environment Steve was operating in changed, and his business model no longer works. And while you could sorta-kinda say it's Sally's fault, you can't say she did anything wrong either legally or morally or in a holistic sense for everyone as a whole, and so there is nothing anyone else should do about it. Steve had no special right to his cakes being purchased. He has the right to offer them, but no one is obligated to buy them, and no one is obligated to care if he fails to sell enough to live well on.

I don't expect anything related to Arm, and neither can anyone else. It's just a totally irrelevant question.

I think the real value isn't so much to do with the Free-As-In-Beer aspects, and more to do with the Free-As-In-Freedom aspects. Having so much open documentation and off the shelf capabilities is like a superpower, and you're starting to see it with stories like these:

https://riscv.org/blog/2020/11/13-year-old-nicholas-sharkey-...

We've got kids designing their own cores. That was a bar that previously was out of reach to anybody without a nine-figure engineering payroll. That's amazing.

Not really, students have been designing RISC cores as long as RISC has been around. It's a standard exercise.

RISCV does make it a bit easier and gives you a clean ISA but it hasn't really had that much of an influence due to its own design i.e. it's caused people to herd around it so there's lots of tutorials and work to borrow floating around.

Having a relatively sophisticated core you can take off the shelf and modify for your own research can be incredibly useful in academia, I would have really liked that when I was doing my thesis. For large companies too who might want particular new instructions or sets of features that are best suited to their own use cases.

SPARC has been open source since 2005, complete with high quality implementation released in 2006. 64-bit, 8 cores, 32 hyperthreads, rising to 64 by 2007. Simulator also provided.

SPARC was able to run Linux and Solaris, and used by Sun in their servers that powered much of the commercial internet in late 90s and early 2000s (before x86 Linux took over).

There have been a few others since then. So relatively sophisticated open source cores for study and modification have been around for many years by now.

It looks to me like the difference with RISC-V is that a larger community has formed around it due to smart organisation and the timing being right, rather than availability.

This is because the underlying CAD tooling has gotten much smarter and easier to use. It's not because of anything RISCV did in particular.

This toolchain enables going from knowing nothing to a core in one class. One doesn't even need to enroll in the class to follow along.

See: https://ocw.mit.edu/courses/electrical-engineering-and-compu...

Surely it is because of the open source ecosystem, especially open-source tooling, reaching a critical mass?

From article: “The open-source community developed key tools that are crucial to make RISC-V-based processors ubiquitous, such as chip technology process design kits, design verification suites, implementation tools, and more”

Closed source tooling was available and “smart”, but licensing, cost, and inflexibility were significant roadblocks. Disclaimer: I don’t work in the industry.

I think to really have the conversation we would have to define the terms. Much of the original CAD tooling was open source because it was written at Universities.

Things like: is it enough for one to make any core or does one have to make the "best" core? If it just has to exist that was pretty much always possible. Definitely not the lowest friction way to go. But possible.

For example here is basic MIPS core originally written in 2003, from chapter 1 of a common VLSI textbook: http://pages.hmc.edu/harris/cmosvlsi/4e/code.html

It's just over 400 lines of verilog and super easy to follow. The tooling changes that happened in the 90s made that possible.

I experimented making cores that were taped-out in my University, as an undergraduate, in the late 90s. It didn't cost my University even close to 9 figures. It was definitely a lot harder than now but the designs were also a lot more modest. Things, essentially untrained, students can do now would've been unthinkable then.

Stands to reason then that they are not designing in the same sense, but configuring and customizing. People have been doing that for a while now on FPGA, or in hardware with 8080, and it's hardly anybody's kids. What's so "amazing" about it?

Dumb cores are a commodity now, which progressed in horsepower from their ca. 60 years old ancestors. I.e. the core is hardly innovative, so what is so amazing about it, technically?

Also, waiting for IP is a huge bar for entry.

Suppose you just want a soft core for a one-off FPGA project. RISC-V is a no-brainer if you need to run complex stuff like a Linux kernel. There's myriad of projects to pick from on GitHub. Try them all, pick the one you prefer.

The barrier to entry is so much reduced that you can use RISC-V "by accident" without having considered it in advance, as part of a normal engineering process in companies of any size, vs months-long waits for IP, after deciding it was worth obtaining.

This all rests on the several suppositions including:

- Arm has no IP that can’t be quickly replicated by other firms (for very little money).

- That the quality of designs from other firms will be better than those from Arm (or for the architecture licensees their own).

- The really big Arm licensees would see a commercial advantage to switching.

Intel threw billions at the smartphone market and still lost against Arm. Today there are zero RISC-V smartphone designs. That may change but probably largely because of the Arm China and Nvidia missteps.

I expect (and look forward to) RISC-V establishing a presence in the market but this sort of commentary does the ISA no favours.

Edit: I see elsewhere you think they should abandon the Arm ISA in favour of RISC-V! really not sure about that ..

1) Intel is/was handicapped by using an old CISC ISA which has some cost in power/performance. This complex x86 decoder ain't free.

2) Network effect favoured ARM.

Intel also had the advantage at the time of a clear process advantage which almost certainly would have more than offset the decoder cost.

Nothing in life is ever simple...

> With ARM, You have to pay ARM for ISA license

This is only true for some definitions of ARM. See for example:

https://en.wikipedia.org/wiki/Amber_(processor) "The Amber core is fully compatible with the ARMv2a instruction set and is thus supported by the GNU toolchain. This older version of the ARM instruction set is supported because it is not covered by patents, and so can be implemented with no license from ARM Holdings"

> Frankly, unless ARM does radically change their business model, I do not expect them to survive.

Looks like someone is having similar thoughts inside ARM. https://hackaday.com/2018/10/02/free-arm-cores-for-xilinx-fp...

There are other efforts too.

If it becomes an issue ARM probably will change dramatically, however keep in mind RISC-V let's you licence hundreds of probably pretty crummy cores (and a handful of good ones) whereas ARMs are battle tested, verified, and come with documentation. RISC-V docs are still a bit 1980s i.e. as far as I'm aware there's no official online source of HTML docs, and not as much blessed software as arm (i.e. compilers tested in-sync with the ISA). Oh and people to sue...

I also trust the ARM ISA designers more than the RISC-V ones, but I don't know enough that you should trust me.

As a hobbyist I see this from a very different perspective. ARM documentation is overwhelming and ironically ARM is confusing as hell to read about due to its fragmentation into 32-bit and 64-bit ARM as well as Thumb1 and Thumb2. I don't have a great memory, and I really get lost when reading ARM tutorials and docs.

RISC-V for hobbyist like me is just WAY WAY easier to deal with. There is a great consistency between RISC-V 32-bit and 64-bit which ARM lacks. There is just one compressed ISA and it maps to the regular one in straight away manner. Register naming is more sensible and consistent.

ARM instructions with their complex addressing modes are not easy to read. ARM vector instructions makes your head explode trying to keep all the details in your head at the same time. RISC-V vector instructions are just way easier to grasp.

In many ways it reminds me of the documentation situation with Python vs Julia. Python has more documentation for sure, but a big problem with that is all the stuff that is outdated irrelevant, combined with the difference between Python 2.x and Python 3.x although that has gotten easier in recent years.

New technologies will always have less documentation but they often benefit from not having lots of legacy which complicates understanding.

At least ARM is easier than x86, but that is a pretty low bar.

The year is 2012. Blender is an open source 3D modeling and CG software. There are hundreds of crummy plugins and hacks (and a handful of good ones,) whereas Maya is battle tested, developed by professional Autodesk engineers. It comes with good documentation and support. Blender documentation and tutorials were essentially youtube videos with cheesy electronic music in the background. (I'm probably getting some details wrong, but you get the point.)

You're not wrong in your assessment. However you're looking at it as it is right now, as opposed to where it's headed for in the future and what it could ultimately become. While CG and computer hardware are very different fields, the effects of communal knowledge sharing are very similar and very powerful. When bored high schoolers and broke college kids (and curious adults) can tinker with the tech, they enter the industry with that much more experience and/or have another avenue for career transition. And that is far more valuable than the mild (and sometimes nonexistent) conveniences of ARM over RISC-V.

Writing code for Blender != Developing a high performance core that is going to be fabricated on TSMC's leading edge process.

In the first case anyone with the right skills can do it. In the second you need access to lots of specialist tools / proprietary industry knowledge.

If RISC-V 'wins' in application processors it will be because an Intel or a Qualcomm invests (probably) hundreds of millions in building a team that works on a multi year project. It definitely won't be bored high schoolers.

Who says you have to fabricate a RISC-V processor on leading edge TSMC nodes? What about FPGAs? What about older nodes? The whole point of my argument is that when you make the proprietary "industry" knowledge more generally available, more people can contribute to the ecosystem as it removes barriers to entry.

> In the first case anyone with the right skills can do it. In the second you need access to lots of specialist tools / proprietary industry knowledge.

In the first case, it used to require specialist tools like the Autodesk suite, and people had to have access to that software to develop the right skills and acquire the industry knowledge.

I don't think RISC-V "winning" is the right way of measuring success. Whether or not it becomes the dominant ISA for everything is irrelevant. It serves an important role in our market and it doesn't need the guys at Qualcomm and Intel to use it to make it successful. Either way Intel is investing big money into RISC-V: https://www.zdnet.com/article/intel-invests-in-open-source-r...

Also, careful what you say about high schoolers: https://riscv.org/blog/2020/11/13-year-old-nicholas-sharkey-...

Fair enough and I don’t disagree at all but I do think it’s a bit different to software development on that there is probably a limit to how far you can go without one firm spending serious money. As you say it may be Intel - which doesn’t really give me a warm glow.

Shockingly this is not strictly the case anymore and it's become less true everyday.

https://info.efabless.com/press-release-efabless-launches-ch...

130nm - that was leading edge 20 years ago.

That means we are only 20 years away from running everything on opensource hardware.

I'm sorry to say there does seem to be a certain lack of respect for the Arm ISA designers floating around. Arm v8 is in billions of smartphones and powers the core with the fastest single threaded performance out there, but somehow it's obviously inferior and will be supplanted.

> I'm sorry to say there does seem to be a certain lack of respect for the Arm ISA designers floating around.

I was going to use that exact wording in a different comment but decided against it, spooky

That is spooky!

I mean there was clearly a lot of analysis put into aarch64 - which probably involved Apple etc - but I've seen comments previously saying they obviously got it wrong because [insert some headline design decision].

They might have got it wrong but they're definitely not amateurs at this and you can't prove anything with a one line comment.

I guess the point is, given the eye balls RISC-V is going to attract, you'd have your Tencents and Apples of the world pouring resources into it, just like they did with AARCH64. And when that happens, where does ARM, as a company, go? They did to Intel what RISC-V is poised to do to them, may be in a decade or two.

I feel ARM could go the Docker way, who faced a similar foe in the stakeholders seeking to commoditize their core business... ruthlessly stomped on them, creating k8s, runc, registries, microvms, serverless, and what-not. Despite Docker having stellar engs working for them (and in some cases, better tech: Swarm, for instance), there's nothing they could do.

Why would Apple pour resources into it? To save a few cents licensing costs on a $1,000 smartphone and give up a decade of hardware and software investment. Sorry, not buying it.

Apple already have a "We can do whatever the fuck we want" licence on aarch64 anyway, notice how they've been adding their own instructions?

> you'd have your Tencents and Apples of the world pouring resources into it

The Tencent and Apple of the world are...Tencent and Apple.

If Amazon say decided to throw billions at developing a Graviton 4 using RISC-V...they really couldn't leverage much of their previous Graviton development work. They also wouldn't have a deep bench of low level RISC-V wunderkind to bring on board to leverage the new platform. It's a chicken and egg problem.

Why would Amazon then want to pay to bootstrap a whole RISC-V market? That's a lot of CapEx without a clear potential for returns. You'll note they did develop Graviton using the ARM ISA so they didn't have to create from whole cloth a "Graviton" market.

Amazon made the same decision as PC makers in the 80s. They consolidated around the IBM clone architecture to take advantage of the rest of the market, especially Microsoft and IBM, supporting the IBM clone market. Commodore, Atari, and Apple all had to fight uphill against IBM clone market.

I haven't seen any technical advantage of RISC-V over ARM that would suggest it's worth pouring billions of development dollars into. It might make sense for Western Digital for drive controllers but not phone, tablet, PC, or server makers.

AFAIU all the Graviton chips so far are using off the shelf cores licensed from Arm. What Amazon is doing is assembling a shopping list of cores, peripherals (probably also to a significant extent licensed from Arm rather than a 3rd party or even in-house) etc. and creating a SoC, which is manufactured by someone else. Even this is no walk in the park, I'm sure Amazon has hundreds(?) of engineers working on Graviton.

Now, if someone would create a RISC-V core competitive with the Arm server cores, and an ecosystem of RISC-V compatible peripherals (well, not compatible in the sense that some random peripheral would need to care about the ISA, but that Arm might not want to licenses their peripherals to a RISC-V based project?) shows up, I'm sure Amazon could do roughly the same with a hypothetical RISC-V Graviton. But if you're talking about designing a RISC-V core from scratch, that's a whole different ballgame.

> AFAIU all the Graviton chips so far are using off the shelf cores licensed from Arm. What Amazon is doing is assembling a shopping list of cores, peripherals (probably also to a significant extent licensed from Arm rather than a 3rd party or even in-house) etc.

This is my point. Amazon using ARM lets them tap into the huge ARM ecosystem with minimal investment on their part. The cores they're using have known qualities and meet whatever performance targets they want.

At this point RISC-V doesn't have that same ecosystem. It doesn't even have extant high performance cores someone can just order. Building momentum is expensive. If selling that ecosystem isn't your main business it's probably not worth investing millions or billions to develop it.

> I haven't seen any technical advantage

RISC-V has geopolitical advantage however in that it's not controlled by US/UK.

I can see why Amazon wouldn't pay to bootstrap that, but I can see why Tencent/Huawai/Alibaba would try to.

> Frankly, unless ARM does radically change their business model, I do not expect them to survive.

I kind of agree, but it’s not straightforward. ARM’s growth wasn’t so much a hockey stick as a more continuous curve with a small exponent. Yes, they only started in 1990, but that was itself a reboot/restart after acorn’s 12 years of effort. And they were scrambling hard for every deal for at least another 15 years.

The environment in which RISC-V emerged is different, of course, but many of the dynamics are still the same. Car companies were still using 16 and even 8 bit devices into the 21st century.

Secondly, ARM has a large arsenal of patents that go along with the license, and they continue to add to the load.

I bear ARM no ill will but I also want RISC-V to supplant them. I just don’t think it’s automatic.

Their business model was to be sold to NVIDIA, but that didn't work out.

Anyway, that's all well good, but - does anyone end up making decent RISC-V processors that could replace a desktop CPU, or a RPi CPU, or something weaker but not in a small niche? Or is this still a vision for the future?

>does anyone end up making decent RISC-V processors that could replace a desktop CPU

As of November, a large number of extensions got ratified, including the vector extension, cryptography acceleration, hypervisor support and other important features.

RISC-V is finally not missing any important feature ARM or amd64 have, and it does it with an order of magnitude lower number of instructions (equivalent but simpler, i.e. better) and with significantly higher code density.

However, test chips with the first designs implementing all of that will take time, even assuming they were tapped out right then, after confirming no last minute changes.

High performance cores depend on these extensions, so we'll begin to see them soon. We know multiple such efforts exist.

Tenstorrent has one such project, led by Jim Keller.

>Their (ARM) business model was to be sold to NVIDIA, but that didn't work out.

They intend to go public now. I recommend against buying those shares, as I do not expect ARM to turn around.

> with significantly higher code density.

This is not correct and is a known weakness of RISC-V at the moment. The ARM toolchains are really good and have decades of improvements in them. This is a big issue for those who need to buy ROM in volume.

Better tools are coming online though. For example:

https://blog.segger.com/code-size-closing-the-gap-between-ri...

"One of the issues faced by RISC-V developers is that the code density of the RISC-V instruction set for deeply embedded processors does not match that of Cortex-M with existing tools."

> RISC-V is finally not missing any important feature ARM or amd64 have, and it does it with an order of magnitude lower number of instructions (equivalent but simpler, i.e. better) and with significantly higher code density.

This has historically been a problem with RISC-V and it’s not really something you’ve backed up as being improved.

> […] an order of magnitude lower number of instructions (equivalent but simpler, i.e. better) […]

I am not sure how to parse the «simpler, i.e. better» part; simplicity vs betterness is orthogonal at best and is contradictory at worst.

Very few people write meticulously handcrafted, highly optimised code for any ISA today, and the compiler writers actually prefer a more complex ISA as it becomes easier for them to transalate high level programming abstractions into an efficient concrete hardware implementation and run it through an optimising pass. Simplicity of the ISA does not immediately translate into faster or more optimised code.

Moreover, creating a highly efficient optimiser is no easy feat as it depends on a large variety of factors and the in-depth knowledge of a specific CPU incarnation: the knowledge of each instruction's timing, instruction interdependencies (i.e. the most optimal instruction sequence that does not stall the pipeline or maximises the ALU/whatever utilisation etc etc), L1 I and D cache line sizes, the knowledge of a particular CPU model / generation… – and that is just a beginning. There is a good reason why Intel, AMD, IBM, ARM et al publish hefty optimisation guidelines / documents for each generation of their CPU's with the compiler writers in mind: the same sequence of instructions issued for the CPU model 123 might be less (or more) efficient than in the next CPU model 456 and vice versa; moreover (e.g. specifically for Intel vs AMD), a sequence of instructions optimised for a particular Intel generation might underperform for an equivalent AMD model or vice versa. Same is likely to be true for different RISC-V core designs from different RISC-V vendors. This is the reason why -mcpu=XXX and -mtune=YYY exist in GCC and clang/LLVM: efficient low-level code optimisation is a tricky business and depends on a large number of compounding factors.

It remains to be seen how the optimisation will be tackled in the RISC-V case with its potpourri of optional ISA extensions and also with the instruction fusion. Given that a random concrete RISC-V implementation can be a combination of the base ISA + a random permutation of any RISC-V extensions (in the worst case scenario), emitting the code that will run equally efficient across N different RISC-V core designs appears to be problematic. Instruction fusion can pose another challenge as a fused macro-instruction may or may not run as efficiently on a RISC-V instance that does not fuse them. There is no guarantee that the compiler generated / optimised code will be equally highly performant across different implementations even for the same set of ISA extensions.

>and the compiler writers actually prefer a more complex ISA as it becomes easier for them to transalate high level programming abstractions into an efficient concrete hardware implementation and run it through an optimising pass.

Itanium aka the Itanic demonstrated this is not the case.

What remedie do you recommend against buying those shares, though?

My take is that RISC-V is not that great of an architecture and might never compete at the high end. (e.g displace ARM, Intel, POWER, etc.)

On the other hand there is a vast market for low-end CPUs that have specializations to be disk controllers and things like that. If the ISA and all the IP required to make specialized devices is free and particularly if there is a culture in which it is easy to learn how to do that then RISC-V will have a special place.

My next spatial computing project is going to be RP 2040 based mostly because I have the parts in stock (other projects are blocked because of supply chain issues) but I am really an AVR8 fanatic and the only path forward I see to higher performance AVR8 systems is a soft core running on an FPGA where very hard tasks (vision? comms?) get offloaded to the FPGA and that can be a very appealing architecture where somebody might prefer RISC-V particularly if the tooling and accelerator integration are there.)

> might never compete at the high end. (e.g displace ARM, Intel, POWER, etc.)

It might also be successful, even in that segment. The RISC-V ISA was specifically designed to scale up (e.g. to OOO and vector processors) while still being very simple, especially at the low-end - a basic RV32E is really comparable in complexity with many real-world 8- and 16-bit chips.

The pretty minimal RV32EC core Ibex is estimated 15k gates: https://github.com/lowRISC/ibex

But, the similarly minimal Arm Cortex M0 is, drumroll, 12k gates.

Not saying this means Arm is better than RISC-V, such a small difference can probably be explained by some microarchitectural feature or lack of it. Just that you can scale down Arm as well.

But yes, I can see tiny chips like these putting a squeeze on 8 and 16 bit microcontrollers.

>My take is that RISC-V is not that great of an architecture

That's not the impression I got, when I studied the specification.

Do you care to elaborate?

See https://gist.github.com/erincandescent/8a10eeeea1918ee4f9d99...

From your statement, I thought you had looked into it yourself.

I remember reading that ex-ARM employee's take back then, when it was discussed here[0]. It was based in a pre-standard version of the ISA which was already old at that point in time, and also ignored the rationale behind many of the decisions it criticized.

By objective metrics (simplicity of instruction set, features available, code density, absence of µarch assumptions), I find RISC-V to be the best general purpose ISA available at the present time.

[0]: https://news.ycombinator.com/item?id=24958423

These objective metrics are not even close to being tested at the moment, whereas aarch64 has made noticeably different decisions guided by real life. They might be wrong but I can't see confidently say riscv is actually better other than simplicity.

If the macro fusions don't work for example that's a pretty dramatic blow against RISC-V compared to aarch64. Similarly code density is a tradeoff because riscv's simplicity means more instructions in the first place i.e. requires actual battle testing first.

Jim Keller is overseeing a very large RISC-V core that should be around the same performance level as X1 or Zen 3. I guess we'll see what the ISA can do pretty soon.

He said they were talking about open-sourcing the CPU block. If they did (the CPU isn't their core business), we could see lots of RISC-V competition popping up. The age of CPUs being commodity items seems to be approaching.

https://youtu.be/KOHQQyAKY14?t=494

That is definitely a phat core but I wouldn't expect it to be exactly trading blows with Zen3 or alder lake given (that depends on one's definition of "around the same" I suppose) since the backend seems quite narrow. That might be all they need for AI however, going to watch the video tomorrow. It has big caches by the looks of things but the throughput is more like Zen2 depending on what they can clock it at.

Either way I don't think anyone is seriously arguing you can't make a high-performance RISC-V process, but the thing is that scaling from (say) fast at memory and basic integer operations all the way up to all the sometimes wacky shit people want from their desktop machines will probably not be easy. It took Apple decades to do it with an ISA they helped design themselves.

https://images.anandtech.com/doci/15813/A78-X1-crop-23.png

They didn’t mention how many branch units they have, but the ALU count is identical to X1.

They have half the SIMD units, but each unit is twice the width which increases instruction density on high performance workloads.

They are planning to open the Small CPU core, the packet processor and the vector processing unit. NOT the actual high performance RISC-V core.

I also think the high performance here is a relative term to their small core.

The bitmanip extension that is scheduled to be part of the RVA22 profile will contain add with shift instructions (d= a + b<<c), which should obviate the need for one of the more common issues that otherwise would need fusion.

I thought that at first but the truth is that x86 and ARM are stuck in a certain mindset, their instruction sets are so complicated it is impossible to mix compressed and uncompressed instructions. Once you consider compression then RISC-V is on average slightly denser than x86. Compression will be everywhere by default.

The only really janky part is the fusion of more than 3 instructions. Now that is insane. However, it is like energy storage for renewables. Once you have an electric grid that can store days worth of energy that's actually extremely amazing. The old way of doing things will be viewed as something cavemen or barbarians did. If macro op fusion scales beyond 3 instructions then RISC V will easily beat other architectures because 2 is the limit for every other architecture.

>Once you consider compression then RISC-V is on average slightly denser than x86.

A note for those not following: RISC-V as in RV64GC. x86 as in 32bit x86.

64bit x86 aka x86-64 aka amd64 is dramatically worse in code density.

High end today requires specialized chips. E.g. if you want massive parallel processing you would want small cores, because you can make more of those. RISC-V gives that kind of flexibility of designing minimalist cores which can then be repeated a thousand times on a silicon die. The same thing that are beneficial for cheap specialized hardware is also often beneficial for high-end stuff, where you really need parallelism to push performance.

Whether you are designing a server chip or machine learning powerhouse it is all about having lots of cores. To get more cores you need smaller cores and RISC-V has demonstrated they can make small cores of half the size of an ARM core with similar performance.

RISC-V simplicity really starts paying off once you go very small.

Jim Keller's team is creating a 6-wide issue RISC-V CPU. It should have similar IPC as ARM X1 or AMD Zen 3.

https://youtu.be/KOHQQyAKY14?t=494

here's an 8-issue design:

https://moonbaseotago.github.io/

There are rumours of Apple being interested with RISC-V. May be MacBook 2030 will feature it.

Apple posted job advertisements looking for RISC-V technical roles.

What they plan to do with them is unknown, but Apple has the cash flow to try a lot of things.

I would expect them to quickly adopt it for embedded applications, and experiment with making their own high performance design, including porting MacOS and Rosetta Stone. They can afford to do this much, regardless of whether they end up moving their main CPUs to RISC-V or not.

I would imagine apple actually ships hundreds of devices with processors - each dongle and peripheral has at least one.

Yep. There's surely a bunch of uses of RISC-V that have little or nothing to do with the main CPU, even in a conventional machine.

Trust modules, device controllers, smart adapter cables etc.

For what it's worth, Apple always has people on hand monitoring innovations in technology and testing their stack on new hardware, most of which never sees the light of day.

See OS X on Intel being a thing inside Apple for years and years before they decided it should see the light of day.

NEXTSTEP was multi-architecture even before Apple owned it.

Probably for future research if they intend to try to smear campaign it :-)

Apple had a big part in aarch64 being what it is today so I am quite skeptical they'd just jump ship.

I might be making this up (I can't remember the company) but I'm pretty sure at least one chip designer has moved from risc-v to arm. It's not clearcut.

Making a RPi equivalent would require a GPU with Linux support, I don't see any sign that RISC-V chip vendors are able to do this.

Building a desktop system with a PCIe graphics card would be easier.

There actually exists at least one GPL-licensed GPU core (GPLGPU), but it's based on a 90s PC 3D accelerator that's really just not that good.

I believe the team behind LibreSOC is also working on a 3D processor, but I don't know how far along they are.

However, if a vendor instead ships a decent framebuffer and high-performance vector unit, I think LLVMpipe would not be a problem for most RPi-equivalent use cases, either light desktop use or server use (especially the latter!)

Isn't Imgtec doing that?

Where can I get the source code for PowerVR kernel drm code from?

https://www.phoronix.com/scan.php?page=news_item&px=Open-Sou...

Nowhere because it's not available yet. They only made a few announcements.

This has since changed. They've released a DRM/DRI driver.

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