Discussion RISC V Latest Developments Discussion [No Politics]

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DisEnchantment

Golden Member
Mar 3, 2017
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Some background on my experience with RISC V...
Five years ago, we were developing a CI/CD pipeline for arm64 SoC in some cloud and we add tests to execute the binaries in there as well.
We actually used some real HW instances using an ARM server chip of that era, unfortunately the vendor quickly dumped us, exited the market and leaving us with some amount of frustration.
We shifted work to Qemu which turns out to be as good as the actual chips themselves, but the emulation is buggy and slow and in the end we end up with qemu-user-static docker images which work quite well for us. We were running arm64 ubuntu cloud images of the time before moving on to docker multi arch qemu images.

Lately, we were approached by many vendors now with upcoming RISC-V chips and out of curiosity I revisited the topic above.
To my pleasant surprise, running RISC-V Qemu is smooth as butter. Emulation is fast, and images from Debian, Ubuntu, Fedora are available out of the box.
I was running ubuntu cloud images problem free. Granted it was headless but I guess with the likes of Imagination Tech offering up their IP for integration, it is only a matter of time.

What is even more interesting is that Yocto/Open Embedded already have a meta layer for RISC-V and apparently T Head already got the kernel packages and manifest for Android 10 working with RISC-V.
Very very impressive for a CPU in such a short span of time. What's more, I see active LLVM, GCC and Kernel development happening.

From latest conferences I saw this slide, I can't help but think that it looks like they are eating somebody's lunch starting from MCUs and moving to Application Processors.
1652093521458.png

And based on many developments around the world, this trend seems to be accelerating greatly.
Many high profile national and multi national (e.g. EU's EPI ) projects with RISC V are popping up left and right.
Intel is now a premium member of the consortium, with the likes of Google, Alibaba, Huawei etc..
NVDA and soon AMD seems to be doing RISC-V in their GPUs. Xilinx, Infineon, Siemens, Microchip, ST, AD, Renesas etc., already having products in the pipe or already launched.
It will be a matter of time before all these companies start replacing their proprietary Arch with something from RISC V. Tools support, compiler, debugger, OS etc., are taken care by the community.
Interesting as well is that there are lots of performant implementation of RISC V in github as well, XuanTie C910 from T Head/Alibaba, SWerV from WD, and many more.
Embedded Industry already replaced a ton of traditional MCUs with RISC V ones. AI tailored CPUs from Tenstorrent's Jim Keller also seems to be in the spotlight.

Most importantly a bunch of specs got ratified end of last year, mainly accelerated by developments around the world. Interesting times.
 

DrMrLordX

Lifer
Apr 27, 2000
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Phoronix benchmarked speed improvements going from Ubuntu 21 to 24 on P550 board running an U740 CPU.

Summary (take with care, I only use the aggregated score, look at individual tests for a more to the point comparison):
1. Ubuntu 24 is 23% faster than Ubuntu 21; most of the speedup seems to come from maturing compilers
2. The R-V board performance is ~10% that of a Pi 500.

I insist, take these results with care.


Are those results from the P550 , or is that from the older Unmated Unmatched board from 2021?
 
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DrMrLordX

Lifer
Apr 27, 2000
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Biggest additional info, not present in the slides: They plan to release a Athena (8x Ascalon) devboard and even laptop for people to buy as a development platform.
8c Ascalon would be very interesting! Any word on pricing and availability?
 
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soresu

Diamond Member
Dec 19, 2014
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The talk is up on youtube:

Biggest additional info, not present in the slides: They plan to release a Athena (8x Ascalon) devboard and even laptop for people to buy as a development platform.
I love it how people never seem to actually hear how atrocious the mic output sounds and fix it in so many of these conferences.
 
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Jul 27, 2020
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Much better but still barely able to match a 4 yo Pi 400.

The HiFive Premier P550 performance relative to the Raspberry Pi ARM SoCs was also all the more impressive when considering it ran at a consistent 1.4GHz across its four cores compared to the Raspberry Pi 4 at around 1.7GHz and the Raspberry Pi 500 at 2.3GHz.

It is clearly faster in some benchmarks. I think the LPDDR5 latency is hurting it. With quad channel DDR4-3600 or dual channel DDR5-8000 CL38, it could do a lot better.

He's our only hope.

No, there's another.
 

DrMrLordX

Lifer
Apr 27, 2000
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It is clearly faster in some benchmarks. I think the LPDDR5 latency is hurting it. With quad channel DDR4-3600 or dual channel DDR5-8000 CL38, it could do a lot better.

I think it only beat the competition on one benchmark. In any case, it's not likely that we'll see any sbcs or dev boards with full DDR4/5 implementations. What would be nice would be a P870 dev board since that should be the current gen chip from SiFive.
 
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soresu

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Sorry but that game controller looks a bit naughty.
Off to horny jail with you....

giphy.gif
 
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soresu

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Dec 19, 2014
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An HPC accelerator / GPU with RISC-V. Why does that remind me of Larrabee that lead to Xeon Phi?

Vaporware at this point (dev kit by Q4'25), but worth following.

It seems to be specifically targeted at ray/path tracing and some niche EMI related computational loads.
 
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DZero

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Jun 20, 2024
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EDIT: Since is politics, I decided remove it, but China's desicion bugs me a lot. Maybe that is the catalyzer to see finally phones of bigger brands like Huawei or Xiaomi using RISC-V chips. At least in low tier.
 

Nothingness

Diamond Member
Jul 3, 2013
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@soresu @DrMrLordX that's my take too (and why I put HPC first, though I should have added RT given the HW for handling tracing) contrary to the title of the article. Given the FP64 focus this could be a good GPGPU beyond RT. Time will tell :)
 
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soresu

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With those specs, nobody's gonna use that for display purposes. It purports to be much faster than a 5090 in fp64 etc.
IIRC FP64 has usually been nV's pain point relative to AMD too, when CDNA1 came that was really the only thing they did particularly well.
 
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Nothingness

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IIRC FP64 has usually been nV's pain point relative to AMD too, when CDNA1 came that was really the only thing they did particularly well.
At first they reduced FP64 in consumer GPU to segment market, as they didn't want HPC users to run GPGPU code on non pro cards. Now I wonder what the current status is given the focus on AI.

My understanding is that AMD started reducing FP64 on their consumer card after Radeon VII (these cards are still heavily used by end users for running computational code, cf Mersenne prime hunting for instance).
 
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soresu

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My understanding is that AMD started reducing FP64 on their consumer card after Radeon VII (these cards are still heavily used by end users for running computational code, cf Mersenne prime hunting for instance).
Higher rate FP64 was always limited to the halo/enthusiast GPU for AMD.

The only difference now is that it is segmented completely out of the consumer market with CDNA.
 
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soresu

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and now that Callandor
Given Keller transitioned from CTO/President to CEO what will be 4 years before the projected date for Callandor, we can assume his contributions to that µArch engineering endeavor to be very high level/conceptual at best (possibly even non existent given he's not even listed as directly associated with the CPU team).

Leaving Wei-han Lien and his team to do the actual implementation - which at the end of the day is no small thing, as the Mongoose CPU team at Samsung learned when trying to match Apple's 6 wide µArch energy.

Even Keller admits as much about Zen in interviews.
 

Nothingness

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Jul 3, 2013
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Power8?

Power9?

Power10?
So many recent CPUs lack details about their uarch that I wonder if there are not other ones that do some variant of clustering.

Edit: I guess this could be detected by people doing reverse-engineering of uarch, but they likely should look for it.