Can risc v replace x86 or arm?

I don’t know much about risc v other than a few YouTube videos here and there. But with arm getting acquired by Nvidia, is there any hope from risc v for replacing x86 or arm in the desktop and mobile market? X86 is pretty bloated and the future for arm doesn’t look as bright as it did a month ago. So do we realistically have alternatives?

There’s that OpenPower / Talos workstation thingie that Wendel made a video on.

I like the OpenCAPI cache coherent memory sharing stuff on POWER, it’s good someone is thinking about that.

Regardless, I don’t see ARM stopping the sale of soft cores or IP cores for others to use as a basis for their own chips, but Mali GPU stuff might have a more interesting future.


RISC-V is an open instruction set. Implementations are not not necessarily open. But anyone with the expertise can make their own CPU design that implements RISC-V and use the existing code and compilers for it.

So can it replace ARM? Yes in theory. In practice, at the moment, no. The performance is not there because designers haven’t been pushing it. Down in the low end embedded stuff it is working great. Up in the high end performance zone where x86 and Power are right now, it is a long way off.

I have a Raptor Talos II workstation. Dual Power9’s, 8 cores each, 4 threads per core. It is a beast and I love it. Any open source code runs amazingly well. The problems are with precompiled x86 software. It can be emulated but you lose a ton of speed doing that.

But anyway, for high end computing Power is great.


And isn’t ARM a RISC processor?
That can run RISC v.5 ( RISC-V )?
If so, how could it “replace” ARM?

ARM the company sells CPU designs that use the ARM the instruction set. The ARM instruction set is RISC, well, it used to be, as in Reduced Instruction Set Computer.

RISC-V is a consortium that is developing RISC-V the instruction set and architecture. The RISC-V instruction set is RISC, as in Reduced Instruction Set Computer.

So the ARM instruction set could be replaced with the RISC-V instruction set.


No other architecture is going to replace ARM in mobile anytime soon. There’s too many binaries out there which depend on ARM-v7 instructions.

There are lots of options out there. MIPS was a competitor to high-end CPUs like POWER and SPARC back in the SGI Irix days, rendering the Jurassic Park dinosaurs among others. It’s been the higher-performance-than-Arm embedded processor for decades, with some strongholds like router hardware. It’s still got a toe-hold in the higher-end thanks to China developing their Dragon Chip. MIPS was reasonably popular as a competitor to ARM in the PDA days, but lost ground.

POWER and PowerPC is still alive, and ranges from low power embedded systems to mainframes and supercomputers. SPARC is still alive despite Sun’s demise. Some others have died off. PA-RISC, Alpha, SH4, etc, but there are still plenty of architectures around.

You must first define the problem. What don’t you like about x86 and ARM? x86-64 performs extremely well, which is why nearly all competitors have gone away. And there’s low-power versions like the Atom running on 2W while still performing like a just slightly older CPU.

It’s unlikely Nvidia is going to do anything to kill off Arm. There are plenty of licensees whose Arm derivations you could buy, instead. And even if they wanted to do so, you can go back a few years and use an older Arm ISA where all patents have expired, and start from there without anyone’s permission.

See also:

The question is, would NV force ARM Holdings to sell off their Mali GPU line or will NV swallow it up like 3dfx?

If NV sells it off, I would love to see AMD buy the Mali stuff and show Qualcomm how to make OpenSource drivers for a mobile GPU. Even though the Adreno line started with ATi, once Qualcomm bought that, they sure did close it up.

is the question OP intended to put out:

“Can RISC replace CISC?”

If so, I’d say not for now, or at least the next 5 years.

Mostly because of gaming, but if it gets pushed too hard that would be possible.

Even Apple is pushing RISC into its product line so that might be interesting.

It can, but it won’t in the next decade.

So the answers to my questions ( in the order that I asked them ) are …

And …
Well it actually can’t.

In theory yes

In reality - as above its an ISA not an implementation

If you’re willing to live with performance compromises sure.

I doubt any of the Risc-V vendors will be anywhere near Apple or Arm/Nvidia in terms of performance for some time and the toolchain / existing software library isn’t there yet.

Right now we’re talking at least 5-10 years out before they get anywhere close t competitive, IMHO, and ARM/x86 aren’t standing still.

Building competitive CPUs is hard, and anyone going RISC-V is starting from a long way back with a lot of hurdles stacked against them. Those will take time to overcome.

Hey check this out:

I may have been wrong about RISC-V not having high end support.

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I saw that the other day. Maybe NV buying ARM pushed things out faster than normal.

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