5 ms·

High performance RISC-V CPU

40 points by aklsh 4y ago

dmitrygr 4y ago
“High performance” and “leader” are funny claims to make while posting no benchmarks
- slaw 4y ago
  It needs to be manufactured first.
  - dmitrygr 4y ago
    That’s NOT how it works. You can simulate it and state MIPS/MHz, for example. Do your really think that the first time silicon designers find out the performance of a chip they designed is when it tapes out?
    - LeFantome 4y ago
      I would say both perspectives are valid. You are correct that performance is “known” at design time. That said, as this is a new platform a little healthy “believe when I see it” is warranted not just for the performance of this new chip but also about when it will ship and what it will be competing with by then. It looks very promising though.
- LargoLasskhyfv 4y ago
  SPECint 2017 per socket compared to some other chips from: https://www.nextplatform.com/2023/02/02/the-first-risc-v-shot-across-the-datacenter-bow/ https://www.nextplatform.com/2023/02/02/the-first-risc-v-sho...
  - qwytw 4y ago
    This is only theoretical though. Especially no real data on power usage and cost.
    - LargoLasskhyfv 4y ago
      Uhm. There is the mention of 300W under the SPECint bar to the right. For 128 cores of V(ersion?)1. Theoretical, or not. Also the headline: The First RISC-V Shot Across The Datacenter Bow /me morphs into Dark Fader and intones: I find your lack of enthusiasm disturbing… … …
nickpeterson 4y ago
I get the feeling that ARM and RISC platforms are going to screw around for so long that by the time you can buy a system with one in them Intel and AMD will have caught up on performance per watt and made them unneeded.
- ZiiS 4y ago
  ARM already massively outsell x86?
  - vlakreeh 4y ago
    They mean in the markets that x86 is leading in, like desktop, mobile laptops, and server. The server market is particularly interesting as while ARM is gaining market share, it's mostly because Intel is losing market share because their products haven't been up to par in terms of performance per watt that AMD can provide.
    - ZiiS 4y ago
      They may not yet be dominant in those markets; but "by the time you can buy a system" is a bit of a stretch given you can walk out of a Apple store with a strong contender for the best Laptop or spin up the highest performance/$ EC2 A1 instances today.
    - retrac 4y ago
      For about 10 years after the introduction of microprocessors, legacy minicomputer platforms continued to sell on the high end. PCs were too small and slow and not enough IO. But the economy of scale made PC hardware incredibly cheap and it rapidly improved. They got bigger. Eventually, server-sized, competing with minicomputers, which did not have the backing of an architecture used at massive scale. Most servers ended up being based on up-scaled PC hardware, and the underlying architecture of servers (such as x86 processors) ended up reflecting that. I think the same may happen with smartphones/TVs/tablets/etc. Billions of these devices are sold each year, compared to perhaps tens of millions of high-end desktops or servers.
- 4y ago
Tuna-Fish 4y ago
The icache is interesting. One of the high points of RISC-V is that it requires less work in the decode part of the frontend compared to competitors, which can be used to reduce pipeline stages. However, it has the disadvantage that it generally requires more code, both in amount of instructions and in bytes, to do the same work. This is bad both because it requires more throughput on the frontend and because it makes L1i cache efficiency worse. This CPU solves this by making the instruction cache very large. This certainly requires more fetch stages in the pipeline to clock high, which is offset by the simpler decode, probably giving similar results to competitors.
- snvzz 4y ago
  >However, it has the disadvantage that it generally requires more code, both in amount of instructions and in bytes, to do the same work. RV64GC is the most dense 64bit architecture. This means it takes the least bytes of code to do a given task.

40 points by aklsh 4y ago

dmitrygr 4y ago

“High performance” and “leader” are funny claims to make while posting no benchmarks

slaw 4y ago
It needs to be manufactured first.
- dmitrygr 4y ago
  That’s NOT how it works. You can simulate it and state MIPS/MHz, for example. Do your really think that the first time silicon designers find out the performance of a chip they designed is when it tapes out?
  - LeFantome 4y ago
    I would say both perspectives are valid. You are correct that performance is “known” at design time. That said, as this is a new platform a little healthy “believe when I see it” is warranted not just for the performance of this new chip but also about when it will ship and what it will be competing with by then. It looks very promising though.
LargoLasskhyfv 4y ago
SPECint 2017 per socket compared to some other chips from: https://www.nextplatform.com/2023/02/02/the-first-risc-v-shot-across-the-datacenter-bow/ https://www.nextplatform.com/2023/02/02/the-first-risc-v-sho...
- qwytw 4y ago
  This is only theoretical though. Especially no real data on power usage and cost.
  - LargoLasskhyfv 4y ago
    Uhm. There is the mention of 300W under the SPECint bar to the right. For 128 cores of V(ersion?)1. Theoretical, or not. Also the headline: The First RISC-V Shot Across The Datacenter Bow /me morphs into Dark Fader and intones: I find your lack of enthusiasm disturbing… … …

nickpeterson 4y ago

I get the feeling that ARM and RISC platforms are going to screw around for so long that by the time you can buy a system with one in them Intel and AMD will have caught up on performance per watt and made them unneeded.

ZiiS 4y ago
ARM already massively outsell x86?
- vlakreeh 4y ago
  They mean in the markets that x86 is leading in, like desktop, mobile laptops, and server. The server market is particularly interesting as while ARM is gaining market share, it's mostly because Intel is losing market share because their products haven't been up to par in terms of performance per watt that AMD can provide.
  - ZiiS 4y ago
    They may not yet be dominant in those markets; but "by the time you can buy a system" is a bit of a stretch given you can walk out of a Apple store with a strong contender for the best Laptop or spin up the highest performance/$ EC2 A1 instances today.
  - retrac 4y ago
    For about 10 years after the introduction of microprocessors, legacy minicomputer platforms continued to sell on the high end. PCs were too small and slow and not enough IO. But the economy of scale made PC hardware incredibly cheap and it rapidly improved. They got bigger. Eventually, server-sized, competing with minicomputers, which did not have the backing of an architecture used at massive scale. Most servers ended up being based on up-scaled PC hardware, and the underlying architecture of servers (such as x86 processors) ended up reflecting that. I think the same may happen with smartphones/TVs/tablets/etc. Billions of these devices are sold each year, compared to perhaps tens of millions of high-end desktops or servers.
4y ago

Tuna-Fish 4y ago

The icache is interesting. One of the high points of RISC-V is that it requires less work in the decode part of the frontend compared to competitors, which can be used to reduce pipeline stages. However, it has the disadvantage that it generally requires more code, both in amount of instructions and in bytes, to do the same work. This is bad both because it requires more throughput on the frontend and because it makes L1i cache efficiency worse. This CPU solves this by making the instruction cache very large. This certainly requires more fetch stages in the pipeline to clock high, which is offset by the simpler decode, probably giving similar results to competitors.

snvzz 4y ago
>However, it has the disadvantage that it generally requires more code, both in amount of instructions and in bytes, to do the same work. RV64GC is the most dense 64bit architecture. This means it takes the least bytes of code to do a given task.