The RISC-V team was very careful in establishing prior art for every design decision. The patents on ISAs tend to be on their quirks, so keeping things truly minimal helps avoid all of that complexity.
Like a lot of what Sun did, prior open chip designs weren't good enough. Academics starting with a clean slate and a 20+ years of additional experience gives RISC-V real advantages over MIPS and ARM.
The primary advantage is that RISC-V is truly RISC: they have a core ISA that is frozen but extendable. This means that they can have application-specific CPUs with intelligent fallback and full compatibility.
As to why now, well, they came up with RISC-V as a teaching ISA and started getting emails from industry asking why it had changed from last semester. It turns out that chip manufacturing has gotten cheap, with custom runs on 28nm processes going for $30K.
You are correct in that their early target market are co-processors and other niche components. Just getting a license from ARM is 10+ million dollars. But the biggest cost in building your own ISA is investment in software and tooling. RISC-V gives a common foundation for everyone to build on.
However, their intent is indeed to bring competition at every level. Their licensing scheme was chosen specifically to allow big players to create IP and keep the secret sauce to themselves, unlike SPARC V8 and OpenRISC.
Apple creates their own CPU and GPU designs, Google has custom hardware for machine learning, and Samsung is about to overtake Intel as the world's largest chip manufacturer. Why should they keep shelling out billions to ARM, Intel, and AMD just to use their ISA?
> Just getting a license from ARM is 10+ million dollars.
Which license? ARM offers several different models.
> Apple creates their own CPU and GPU designs, Google has custom hardware for machine learning, and Samsung is about to overtake Intel as the world's largest chip manufacturer. Why should they keep shelling out billions to ARM, Intel, and AMD just to use their ISA?
The Google hardware we know (TPU) for learning does not use ARM at all, so they would obviously pay nothing there. BigCo's like Apple or Samsung are probably ARM partners, so no per-design/unit fees.
Samsung Electronics may become the biggest chip manufacturer soon, but much like with smartphones that's only by turnover, not profit. But profit is what ultimately finances your R&D.
An interesting titbit is that even Intel and ARM are, at least on paper, partners.
>BigCo's like Apple or Samsung are probably ARM partners, so no per-design/unit fees.
Nope, all ARM licensees pay a per-unit royalty, regardless of their partnership level[0]. Being the biggest might help Apple and Samsung negotiate a slightly lower royalty rate, but by the end of the day it's still at least 1% of the chip's selling price.
> but by the end of the day it's still at least 1% of the chip's selling price.
Right, but you cannot just consider the difference in royalty fees between ARM and another ISA.
For example, the STM32F* chips cost between $0.60 (STM32F0) [0] and $19 (STM32F7) [1].
You can't just compare the royalty fee here when thinking of lost revenue for the manufacturer. The ARM ecosystem is huge, and if ST switched to another ISA, they would probably lose customers unless the new ISA had an ecosystem that was as good or better than ARM.
Yes, the royalty amount matters, but customer preferences also matter. I doubt any high volume ST customer would be willing to switch to an entirely new ISA without the kind of ecosystem that ARM has for a few pennies per chip. And who is going to pay for the development of the tools? Unless it's someone like RISC-V, then they're probably stuck developing it themselves. Kiss goodbye to all the money you "saved" by not paying ARM royalties.
Furthermore, if ST switched to a different ISA to save the ARM royalty, what makes you think they would pass along that savings to the customer?
Bluespec, AMD, Qualcomm, IBM, NVidia, Micron, NXP, Samsung and a few dozen other companies are all dues paying members of the RISC-V foundation. I think it's possible for them to create a new ecosystem, just give them time.
Apples and oranges. The companies that design the chips and pays royalties for IP are mostly fabless (with rare exceptions like Intel). The fabs are owned by separate entities like TSMC, Samsung, SMIC that specialize in the production itself. The fabs don't pay for CPU IP (they sometimes pay for some other basic IP to be able to offer them as standard to their customers, but that doesn't cover CPUs/GPUs).
About Samsung, they're on both sides but with separate legal entities.
The licensing cost IS usually significant to most fabless companies, who come in many sizes. Most are not as big as Apple or NVidia. The fabless model comes from the very high cost of a modern fab, it allows sharing a fab through many fabless design houses.
ARM has the reputation of being cheap, because the typical IT/software people compare them to Intel. And yes, compared to Intel most anyone is cheaper ;) But in the embedded space, which is cost sensitive, ARM is not cheap. It's like what IBM and Microsoft were in IT: nobody got fired for choosing them, and they come with a very powerful ecosystem. Something they make client pay for.
In front of ARM, one can find good technical competitors depending on the target market (MIPS, Cortus, Andes, Beyond Semi...). But MIPS ecosystem is smaller, and for the others waaaaay smaller.
RISC V has an opportunity in time to provide a good technology, backed by a strong ecosystem, for lower costs. In the embedded space at least, this is a very powerful combination.
The older OpenRISC had already found a few niches. For example, the management core in some of Allwinner's newer ARM SoCs is apparently OpenRISC, presumably because they didn't want to license another lower-end ARM core or something. Similarly, some Samsung TVs apparently use it.
For the costs, they do not only get the license to use the ISA, but the whole processor design, as in the "source code" to the whole processor. As a licensee, you place that design together with any other electronics you create (or license separately) on a chip to create the device you want.
Perhaps I'm misreading your comment, but Samsung is designing its own CPU these days. It doesn't license ARM's Cortex CPUs anymore (at least for the Galaxy S/Note series) - basically it's doing what Qualcomm and Apple are doing, too.
Like a lot of what Sun did, prior open chip designs weren't good enough. Academics starting with a clean slate and a 20+ years of additional experience gives RISC-V real advantages over MIPS and ARM.
The primary advantage is that RISC-V is truly RISC: they have a core ISA that is frozen but extendable. This means that they can have application-specific CPUs with intelligent fallback and full compatibility.
As to why now, well, they came up with RISC-V as a teaching ISA and started getting emails from industry asking why it had changed from last semester. It turns out that chip manufacturing has gotten cheap, with custom runs on 28nm processes going for $30K.
You are correct in that their early target market are co-processors and other niche components. Just getting a license from ARM is 10+ million dollars. But the biggest cost in building your own ISA is investment in software and tooling. RISC-V gives a common foundation for everyone to build on.
However, their intent is indeed to bring competition at every level. Their licensing scheme was chosen specifically to allow big players to create IP and keep the secret sauce to themselves, unlike SPARC V8 and OpenRISC.
Apple creates their own CPU and GPU designs, Google has custom hardware for machine learning, and Samsung is about to overtake Intel as the world's largest chip manufacturer. Why should they keep shelling out billions to ARM, Intel, and AMD just to use their ISA?