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Amid chip shortages, companies bet on RISC-V

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Re: Amid chip shortages, companies bet on RISC-V

#101

Post by ColonelPhantom »

Symmetry wrote: post #39
Reitet00 wrote: post #2

Very nice to see RISC-V growing like that and being in the area of interest by big names such as Google and Intel. Open solutions are critical for risk management but I wonder if desktop/server RISC-V processors are also planned.

The flexibility that makes RISC-V so compelling in embedded roles (what if I want 64 bit address but don't need hardware floating point?) makes it a harder target for the sort of workloads that you'd usually run on a server or desktop. If I were going to create an open high performance core to challenge x86 and ARM's A series cores I'd probably use PowerPC as a base rather than RISC-V. But I do think that RISC-V has…

RISC-V is very flexible, yes, but most 'desktop-class'/application processors are expected to implement at least RV64GC. G is short for IMAFD, so mul/div, atomics, and floating point are all in there, as well as compressed instructions (C) to reduce code size.

Other features you're likely to want are also included in the specification, so if you want to write code that uses for example the B bit manipulation extension or the V vector extension (which is scalable with vector width as well, unlike SSE/AVX) you just have to check a standardized 'CPUID' bit and can run your code, and otherwise fall back to other code.

I also believe that the spec may let operating systems hook these instructions and provide fallbacks so application developers don't have to, but I'm not too sure on the specifics of the privileged ISA of RISC-V.

Re: Amid chip shortages, companies bet on RISC-V

#102

Post by arnaudsm »

Lind5 wrote: post #75

not just the chip shortage. The rise of RISC-V coincides with a couple of other events in the industry. The first is the slowing of Moore’s Law, meaning that increases in total processing power no longer comes along with each new fabrication node. The second is the meteoric rise in machine learning, demanding massive increases in processing power. https://semiengineering.com/why-risc-v-is-succeeding/

Language models and image generation make fun demos, but do we have transformative use cases that'll actually require large ML compute in the future ? Voice recognition and translation are the only ones that comes to mind, yet don't require that much power.

Re: Amid chip shortages, companies bet on RISC-V

#103

Post by [deleted] »

sremani wrote: post #28
xadhominemx wrote: post #25

Earlier quoted context omitted.

High purity quartz is definitely not a bottleneck in the electronics industry.

May be you are right, but can you add some color and context to your commentary. Like a good article link etc. I am more than happy to chance my mind, if provided evidence.

[deleted]

Re: Amid chip shortages, companies bet on RISC-V

#104

Post by stew-j »

crote wrote: post #48
mysterydip wrote: post #29

What I don't get is there's millions of "good enough" e-waste motherboards, RAM, CPUs etc. out there. Wouldn't recycling be better than having nothing or waiting indefinitely? Are there that many workloads that can only run on brand new hardware?

It depends. First of all, we aren't really talking about motherboards or CPUs here. It is embedded electronics, not desktop computing. They are highly specialized application-specific electronics, which require a lot of engineering time to design, validate, and certify. It is nothing at all like the computer ecosystem, where you can just swap in a different motherboard. Boards are designed to use very specific chips,…

Nice writeup, thanks.

> It depends.

I hardly ever give up a computer, we still have a '98 Windows laptop doing recipe duty in the kitchen. (It's getting harder to find a small 32 bit Linux distro these days, though.) Energy efficiency is another concern, one machine I took to be "recycled" (I know--maybe or maybe not) was a Mac G4 which was good as a space heater in the winter, but that's about it--and I didn't feel like moving it 1500 miles with our latest relocation.

I started with electronics many years ago, and would balk at replacing a surface mount chip, but people could learn basic electronic repair literacy for things that commonly break like cords which would help a lot. I also don't tend to buy products like smart phones which are glued together and difficult to repair.

As for RISC-V, it is hard to find even a dev board with the chip shortages (I bought a HiFive Inventor kit to experiment with as a first project):

https://www.hifiveinventor.com/

Re: Amid chip shortages, companies bet on RISC-V

#105

Post by Someone »

cestith wrote: post #95
MobiusHorizons wrote: post #34

Earlier quoted context omitted.

> Exynos Chromebooks and such led the way to ARM Macbooks the same way the IBM PC led to displacing DEC and Sun workstations I think chrome books had very little to do with it. A lot of the work had already happened with the PowerPC switch. On the processor front, Apple’s arm processors aren’t at all like exynos chips that use standard arm cores. I would say that the apple silicon macs are more influenced by iPhone a…

Apple wouldn't have used ARM for the iPhone and iPad if the cores hadn't been proven in other similar platforms. ARM goes back a long time. My Psion palmtops have ARM cores. Many of the WinCE systems have ARM cores. The ARM processors in fact go back to 1985, with the ARM Development System for the BBC Micro and then the Archimedes in 1987. There's a whole world of ARM processors out there. The ISA, packaging, softwa…

> Apple didn't look at the 18 MHz v7 cores from Cirrus Logic in the Psion Series 5 and immediately decide they could make a mainstream desktop CPU out of it.

It’s more likely that Psion looked at the 20 MHz ARM cores that Apple shipped in the Newton and decided they could make a Psion with that.

Re: Amid chip shortages, companies bet on RISC-V

#106

Post by snvzz »

conradev wrote: post #9
worldofmatthew wrote: post #3

I suspect most of RISC-V development is more towards moving away from western controlled ISA's that can be sanctioned for any reason. Points about avoid shortages from any fab being allowed to fabricate RISC-V CPUs is just the "cherry on top".

I don’t know if sanctions are the reason, but moving away from foreign-controlled IP is certainly a thing. Chinese companies make STM32 clones (even fixing the errata in the original): https://hackaday.com/2020/10/22/stm32-clones-the-good-the-ba...

Gigadevices GD32 has a successor in GD32V, which is the same but RISC-V based.

Re: Amid chip shortages, companies bet on RISC-V

#107

Post by snvzz »

oneplane wrote: post #59
pclmulqdq wrote: post #40

Earlier quoted context omitted.

The stolen architectures cannot be legitimately sold outside of China, due to patents held by ARM ltd. RISC-V avoids these headaches.

Indeed, but conversely, China will have access to ARM no matter what. This also means that we can sanction all we want, they locally have the fabs and IP to create ARM, RISC-V, MIPS and even x86 CPUs (and they are already doing all of that). Granted, their fabs can't do top-of-the-line lithography (yet?) but since they have already created 64-core ARM server CPUs and some custom AI silicon they can get horizontally s…

They do have access to ARM, sure. But they also have access to RISC-V, which is technically superior and free of the troubles associated with ARM.

Re: Amid chip shortages, companies bet on RISC-V

#108

Post by brucehoult »

cestith wrote: post #95
MobiusHorizons wrote: post #34

Earlier quoted context omitted.

> Exynos Chromebooks and such led the way to ARM Macbooks the same way the IBM PC led to displacing DEC and Sun workstations I think chrome books had very little to do with it. A lot of the work had already happened with the PowerPC switch. On the processor front, Apple’s arm processors aren’t at all like exynos chips that use standard arm cores. I would say that the apple silicon macs are more influenced by iPhone a…

Apple wouldn't have used ARM for the iPhone and iPad if the cores hadn't been proven in other similar platforms. ARM goes back a long time. My Psion palmtops have ARM cores. Many of the WinCE systems have ARM cores. The ARM processors in fact go back to 1985, with the ARM Development System for the BBC Micro and then the Archimedes in 1987. There's a whole world of ARM processors out there. The ISA, packaging, softwa…

At the very first moment that there was a company called "ARM", in 1991, Apple owned 1/3 of it, the other partners being Acorn(who invented it) and VLSI Technology (who made the chips).

Psion adopted a CPU Apple was using in, AND A COMPANY THEY OWNED developed for, the Newton and eMate, not the other way around. The ARM710 used in the Series 5 was the same as Apple used in the eMate.

Re: Amid chip shortages, companies bet on RISC-V

#109

Post by brucehoult »

Symmetry wrote: post #68
mixmastamyk wrote: post #67

Earlier quoted context omitted.

What are the trade-offs of PowerPC vs RISC-V?

In addition to RISC-V being more flexible than ideal here, PowerPC is more complicated as an instruction set which is a drawback if you're a student learning to implement your first processor or in a deeply embedded role. But given the huge amount of effort that goes into a high performance core it gets lost in the noise and it lets you execute tasks in fewer instructions without crazy difficult to implement levels o…

RISC-V does not in any way depend on instruction fusion. I don't why this meme persists, especially as no RISC-V cores in the market do instruction fusion.

High end OoO cores in other ISAs are BREAKING DOWN complex instructions into µops. RISC-V is pre-broken down. The one exception to that is current x86 and ARM cores DO do instruction fusion, to combine a compare with a following conditional branch. Which is a singe instruction in RISC-V in the first place. SO it is actually the other way around.

Low end cores shouldn't be doing either fusion or breaking down into µops. They are supposed to be as simple as possible, and doing either of those is a complication using significant silicon area and energy.

There might be a place for instruction fusion in mid-range cores. Things in the ARM Cortex A53 / A55 / A510 range. The most popular RISC-V core in that segment, the SiFive U74 (used in the HiFive Unmatched, BeagleV Starlight, VisionFive v1, VisionFive 2, Pine64 Star64 .. and probably more yet to be announced) doesn't fuse multiple instructions into one instruction, but it does pair a forward conditional branch past a single instruction with that following instruction. Both instructions still exist, they each go down one of the two execution pipelines side by side, the same as if the branch was predicted not-taken. At the final pipe stage if the branch turns out to be taken, instead of taking a mis-predicted branch penalty and flushing the pipeline, the U74 simply does not write the result of that following instruction back to the destination register.

That's the closest any currently shipping RISC-V core I know of comes to instruction fusion.

"crazy difficult to implement levels of instruction fusion" does not exist anywhere, and is not needed. It's just an idea from an academic which doesn't actually exist in the real world, at least at present.

Re: Amid chip shortages, companies bet on RISC-V

#110

Post by brucehoult »

yywwbbn wrote: post #74
worldofmatthew wrote: post #16

Earlier quoted context omitted.

Any fab is allowed to produce a RISC-V CPU. You will also have far more core designs that can work across different fabrication possess.

It’s not obvious that any RISC-V CPUs that might be able to compete with ARM/x86 will be free in the future. It would take a lot of money to design them, why would the company that does that just give it away for free?

https://github.com/MoonbaseOtago/vroom

One-man project. It works, right now, at A76 levels. The aim is M1 level, and the bottlenecks to that are known and being addressed.

There is NO WAY one person could do with with a complex ISA such as x86, ARM, or POWER.

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