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> RISC-V will get there, eventually. Not trolling: I legitimately don't see why this is assumed to be true. It is one of those things that is true only once it

> RISC-V will get there, eventually. Not trolling: I legitimately don't see why this is assumed to be true. It is one of those things that is true only once it has been achieved. Otherwise we would be able to create super high performance Sparc or SuperH processors, and we don't. As you note, Arm once was fast, then slow, then fast. RISC-V has never actually been fast. It has enabled surprisingly good implementations by small numbers of people, but competing at the high end (mobile, desktop or server) it is not.

gt0 8mo ago
I don't think anybody suggests Oracle couldn't make faster SPARC processors, it's just that development of SPARC ended almost 10 years ago. At the time SPARC was abandoned, it was very competitive.
- twoodfin 8mo ago
  In single-threaded performance? That’s not how I remember it: Sun was pushing parallel throughput over everything else, with designs like the T-Series & Rock.
  - gt0 8mo ago
    Perhaps not single thread, but Rock was a dead end a while before Oracle pulled the plug, and Sun/Oracle's core market of course was always servers not workstations. We used Niagara machines at my work around the T2 era, a long time ago, but they were very competitive if you could saturate the cores and had the RAM to back it up.
    - twoodfin 8mo ago
      Sure, my work got a few of the Niagaras too and they were tremendous build machines for Solaris software. But if you’re judging an ISA by performance scalability, you generally want to look at single-threaded performance.
- icedchai 8mo ago
  Sparc stopped being competitive in the early 2000’s.
rwmj 8mo ago
RISC-V doesn't have the pitfalls of Sparc (register windows, branch delay slots), largely because we learned from that. It's in fact a very "boring" architecture. There's no one that expects it'll be hard to optimize for. There are at least 2 designs that have taped out in small runs and have high end performance.
- fidotron 8mo ago
  > RISC-V doesn't have the pitfalls of Sparc (register windows, branch delay slots), You're saying ISA design does have implementation performance implications then? ;) > There's no one that expects it'll be hard to optimize for [Raises hand] > There are at least 2 designs that have taped out in small runs and have high end performance. Are these public? Edit: I should add, I'm well aware of the cultural mismatch between HN and the semi industry, and have been caught in it more than a few times, but I also know the semi industry well enough to not trust anything they say. (Everything from well meaning but optimistic through to outright malicious depending on the company).
  - mastax 8mo ago
    I assume the TensTorrent TT-Ascalon is one of the CPU designs.
  - rwmj 8mo ago
    The 2 designs I'm thinking of are (tiresomely) under NDA, although I'm sure others will be able to say what they are. Last November I had a sample of one of them in my hand and played with the silicon at their labs, running a bunch of AI workloads. They didn't let me take notes or photographs. > There's no one that expects it'll be hard to optimize for No one who is an expert in the field, and we (at Red Hat) talk to them routinely.
    - saagarjha 8mo ago
      Expert here, are these made for general purpose workloads or do you expect them to be fast for AI only?
- 8mo ago
lizknope 8mo ago
I think the bigger question is does RISC-V need to be fast? Who wants to make it fast? I'm a chip designer and I see people using RISC-V as small processor cores for things like PCIE link training or various bookkeeping tasks. These don't need to be fast, they need to be small and low power which means they will be relatively slow. Most people on tech review sites only care about desktop / laptop / server performance. They may know about some of the ARM Cortex A series CPUs that have MMUs and can run desktop or smartphone Linux versions. They generally don't care about the ARM Cortex M or R versions for embedded and real time use. Those are the areas where you don't need high performance and where RISC-V is already replacing ARM. EDIT: I'll add that there are companies that COULD make a fast RISC-V implementation. Intel, AMD, Apple, Qualcomm, or Nvidia could redirect their existing teams to design a high performance RISC-V CPU. But why should they? They are heavily invested in their existing x86 and ARM CPU lines. Amazon and Google are using licensed ARM cores in their server CPUs. What is the incentive for any of them to make a high performance RISC-V CPU? The only reason I can think of is that Softbank keeps raising ARM licensing costs and it gets high enough that it is more profitable to hire a team and design your own RISC-V CPU.
- adgjlsfhk1 8mo ago
  Of your list, Qualcomm and Nvidia are fairly likely to make high perf Riscv cpus. Qualcomm because Arm sued them to try and stop them from designing their own arm chips without paying a lot more money, and Nvidia because they already have a lot of teams making riscv chips, so it seems likely that they will try to unify on the one that doesn't require licensing.
  - lizknope 8mo ago
    Yeah, they could but then what is the market? Qualcomm wants to sell smartphone chips and Android can run on RISC-V and most Android Java apps could in theory run. But if you look at the Intel x86 smartphone chips from about 10 years ago they had to make an ARM to x86 emulator because even the Java apps contained native ARM instructions for performance reasons. Qualcomm is trying to push their ARM Snapdragon chips in Windows laptops but I don't think they are selling well. Nvidia could also make RISC-V based chips but where would they go? Nvidia is moving further away from the consumer space to the data center space. So even if Nvidia made a really fast RISC-V CPU it would probably be for the server / data center market and they may not even sell it to ordinary consumers. Or if they did it could be like the Ampere ARM chips for servers. Yeah you can buy one as an ordinary consumer but they were in the $4,000 range last time I looked. How many people are going to buy that?
Findecanor 8mo ago
Because today, getting a fast CPU out it isn't as much an engineering issue as it is about getting the investment for hiring a world-class fab. The most promising RISC-V companies today have not set out to compete directly with Intel, AMD, Apple or Samsung, but are targeting a niche such as AI, HPC and/or high-end embedded such as automotive. And you can bet that Qualcomm has RISC-V designs in-house, but only making ARM chips right now because ARM is where the market for smartphone and desktop SoCs is. Once Google starts allowing RVA23 on Android / ChromeOS, the flood gates will open.
- adgjlsfhk1 8mo ago
  It's very much both. You need millions of dollars for the fab, but you also need ~5 years to get 3 generations of cpus out (to fix all the performance bugs you find in the first two)
snvzz 8mo ago
Fast, RVA23-compatible microarchitectures already exist. Everything high performance seems to be based on RVA23, which is the current application profile and comparable to ARMv9 and x86-64v4. However, it takes time from microarchitecture to chips, and from chips to products on shelves. The very first RVA23-compatible chips to show up will likely be the spacemiT K3 SoC, due in development boards April (i.e. next month). More of them, more performant, such as a development board with the Tenstorrent Ascalon CPU in the form of the Atlantis SoC, which was tapped out recently, are coming this summer. It is even possible such designs will show up in products aimed at the general public within the present year.

gt0 8mo ago

I don't think anybody suggests Oracle couldn't make faster SPARC processors, it's just that development of SPARC ended almost 10 years ago. At the time SPARC was abandoned, it was very competitive.

twoodfin 8mo ago
In single-threaded performance? That’s not how I remember it: Sun was pushing parallel throughput over everything else, with designs like the T-Series & Rock.
- gt0 8mo ago
  Perhaps not single thread, but Rock was a dead end a while before Oracle pulled the plug, and Sun/Oracle's core market of course was always servers not workstations. We used Niagara machines at my work around the T2 era, a long time ago, but they were very competitive if you could saturate the cores and had the RAM to back it up.
  - twoodfin 8mo ago
    Sure, my work got a few of the Niagaras too and they were tremendous build machines for Solaris software. But if you’re judging an ISA by performance scalability, you generally want to look at single-threaded performance.
icedchai 8mo ago
Sparc stopped being competitive in the early 2000’s.

rwmj 8mo ago

RISC-V doesn't have the pitfalls of Sparc (register windows, branch delay slots), largely because we learned from that. It's in fact a very "boring" architecture. There's no one that expects it'll be hard to optimize for. There are at least 2 designs that have taped out in small runs and have high end performance.

fidotron 8mo ago
> RISC-V doesn't have the pitfalls of Sparc (register windows, branch delay slots), You're saying ISA design does have implementation performance implications then? ;) > There's no one that expects it'll be hard to optimize for [Raises hand] > There are at least 2 designs that have taped out in small runs and have high end performance. Are these public? Edit: I should add, I'm well aware of the cultural mismatch between HN and the semi industry, and have been caught in it more than a few times, but I also know the semi industry well enough to not trust anything they say. (Everything from well meaning but optimistic through to outright malicious depending on the company).
- mastax 8mo ago
  I assume the TensTorrent TT-Ascalon is one of the CPU designs.
- rwmj 8mo ago
  The 2 designs I'm thinking of are (tiresomely) under NDA, although I'm sure others will be able to say what they are. Last November I had a sample of one of them in my hand and played with the silicon at their labs, running a bunch of AI workloads. They didn't let me take notes or photographs. > There's no one that expects it'll be hard to optimize for No one who is an expert in the field, and we (at Red Hat) talk to them routinely.
  - saagarjha 8mo ago
    Expert here, are these made for general purpose workloads or do you expect them to be fast for AI only?
8mo ago

lizknope 8mo ago

I think the bigger question is does RISC-V need to be fast? Who wants to make it fast? I'm a chip designer and I see people using RISC-V as small processor cores for things like PCIE link training or various bookkeeping tasks. These don't need to be fast, they need to be small and low power which means they will be relatively slow. Most people on tech review sites only care about desktop / laptop / server performance. They may know about some of the ARM Cortex A series CPUs that have MMUs and can run desktop or smartphone Linux versions. They generally don't care about the ARM Cortex M or R versions for embedded and real time use. Those are the areas where you don't need high performance and where RISC-V is already replacing ARM. EDIT: I'll add that there are companies that COULD make a fast RISC-V implementation. Intel, AMD, Apple, Qualcomm, or Nvidia could redirect their existing teams to design a high performance RISC-V CPU. But why should they? They are heavily invested in their existing x86 and ARM CPU lines. Amazon and Google are using licensed ARM cores in their server CPUs. What is the incentive for any of them to make a high performance RISC-V CPU? The only reason I can think of is that Softbank keeps raising ARM licensing costs and it gets high enough that it is more profitable to hire a team and design your own RISC-V CPU.

adgjlsfhk1 8mo ago
Of your list, Qualcomm and Nvidia are fairly likely to make high perf Riscv cpus. Qualcomm because Arm sued them to try and stop them from designing their own arm chips without paying a lot more money, and Nvidia because they already have a lot of teams making riscv chips, so it seems likely that they will try to unify on the one that doesn't require licensing.
- lizknope 8mo ago
  Yeah, they could but then what is the market? Qualcomm wants to sell smartphone chips and Android can run on RISC-V and most Android Java apps could in theory run. But if you look at the Intel x86 smartphone chips from about 10 years ago they had to make an ARM to x86 emulator because even the Java apps contained native ARM instructions for performance reasons. Qualcomm is trying to push their ARM Snapdragon chips in Windows laptops but I don't think they are selling well. Nvidia could also make RISC-V based chips but where would they go? Nvidia is moving further away from the consumer space to the data center space. So even if Nvidia made a really fast RISC-V CPU it would probably be for the server / data center market and they may not even sell it to ordinary consumers. Or if they did it could be like the Ampere ARM chips for servers. Yeah you can buy one as an ordinary consumer but they were in the $4,000 range last time I looked. How many people are going to buy that?

Findecanor 8mo ago

Because today, getting a fast CPU out it isn't as much an engineering issue as it is about getting the investment for hiring a world-class fab. The most promising RISC-V companies today have not set out to compete directly with Intel, AMD, Apple or Samsung, but are targeting a niche such as AI, HPC and/or high-end embedded such as automotive. And you can bet that Qualcomm has RISC-V designs in-house, but only making ARM chips right now because ARM is where the market for smartphone and desktop SoCs is. Once Google starts allowing RVA23 on Android / ChromeOS, the flood gates will open.

adgjlsfhk1 8mo ago
It's very much both. You need millions of dollars for the fab, but you also need ~5 years to get 3 generations of cpus out (to fix all the performance bugs you find in the first two)

snvzz 8mo ago

Fast, RVA23-compatible microarchitectures already exist. Everything high performance seems to be based on RVA23, which is the current application profile and comparable to ARMv9 and x86-64v4. However, it takes time from microarchitecture to chips, and from chips to products on shelves. The very first RVA23-compatible chips to show up will likely be the spacemiT K3 SoC, due in development boards April (i.e. next month). More of them, more performant, such as a development board with the Tenstorrent Ascalon CPU in the form of the Atlantis SoC, which was tapped out recently, are coming this summer. It is even possible such designs will show up in products aimed at the general public within the present year.