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I need… more powahhh… No but seriously why don’t they build a 128-core atom server. That’s really all anybody wants. I don’t need the fastest most immersed cpu

by booi 4y ago

I need… more powahhh… No but seriously why don’t they build a 128-core atom server. That’s really all anybody wants. I don’t need the fastest most immersed cpu ever, just a bunch of decent ones at 30W or less.

tadfisher 4y ago
That was Larrabee/Xeon Phi, was it not? Discontinued for lack of sales.
- sseagull 4y ago
  That’s basically what I thought. However, IIRC they were marketed more towards high-performance computing (with avx-512). They were an uncomfortable middle ground though, between normal CPUs and GPUs. My benchmarks showed that there wasn’t much of an advantage over 20-ish normal xeon cores (for my HPC workloads). (Memory is a little fuzzy - that was 4-6 years ago).
  - glowingly 4y ago
    While not exactly what you are looking for, Intel Snow Ridge is a continuation of their Atom-based (next to their line of Core-based) networking processors. 8-24 cores. https://www.intel.com/content/www/us/en/products/details/processors/atom/p.html https://www.intel.com/content/www/us/en/products/details/pro... Though, unless if you 100% need X86, there is the Ampere Altra 128 core Cortex-N1 chip.
astrange 4y ago
That’d be a pretty unbalanced architecture - may use less rack space than 128 servers, but with only one servers’ worth of IO, network, PSUs, it’d be less reliable and maybe not even faster.
- booi 4y ago
  A single AWS graviton server is roughly 128 cores with, I believe, 2x or 4x 40gbit networking. It’s not crazy really.
- Dylan16807 4y ago
  One core is probably not pushing more than 100mbit on average. Scaling that much networking up a hundredfold is child's play.
matja 4y ago
AMD's plan with EPYC Zen 4 "Bergamo", with up to 128 Zen 4c cores.
tyrfing 4y ago
128 cores at 30 watts isn't something I've seen anyone planning. What's more likely is 128 cores at 300-400+ watts, and scaling from there is most likely to increase power usage and core counts. Bergamo (AMD), Graviton (AWS), Sierra Forest (Intel), Grace (NVIDIA) are all going for that. 30 watts is low power mobile and "edge" compute.
- booi 4y ago
  You’re definitely right. I meant 30W per cpu or less which usually means maybe 4-8 cpus per host or ~300W. I did mean to compare it to Graviton and will definitely look at the other contenders in this space.
  - tyrfing 4y ago
    Oh OK. Recent server CPUs (Ice Lake) are roughly 8-12W (maybe up to 15W, there are a lot of SKUs) as a baseline. AMD's latest Milan generation brings it down to 3.5W/core, with some closer to 5W; Intel's Sapphire Rapids only goes down to ~ 6W. After M1 and Graviton, there's a big rush for making denser server CPUs, pretty much bifurcating the market. Much more powerful than old Atom cores, but more power-efficient than regular ones, and targeted mostly at hyperscalers. AMD should have a dense variant of Zen 4 out next year, going up to 128 cores and reducing per-core power significantly. Intel will likely have a competitor out in 2024, and AMD might hit 256 cores then, although rumors of things that far out aren't very specific. On the ARM side of things, NVIDIA is launching CPUs like this next year. Qualcomm bought Nuvia, which was working on similar server CPUs, but probably switched focus to PCs. There are some other oddballs like Tenstorrent as well. One interesting part with pushing per-core power so low is that communication between cores starts to be a serious part of total power consumption.
Dylan16807 4y ago
Atoms generally use 3-5 watts per core. So the biggest CPUs they're making are on par with atoms. They keep designing chips that use less and less per core. Why not cram as many cores as possible into a single server? Lower density means more wasted material, and once you go below 2GHz you're not saving very much power any more.
- c_o_n_v_e_x 4y ago
  > Why not cram as many cores as possible into a single server? Manufacturing yields
  - Dylan16807 4y ago
    That's why you limit die size to a certain extent. But that's not a limiting factor on cores per server. You can cram many more 150mm² dies into your server's sockets than you can actually feed with power and cooling and RAM.
    - xxs 4y ago
      A major issue is the cache coherency. If you dont have coherency, effectively you have an architecture that just multiple distinct servers.
      - Dylan16807 4y ago
        You can run coherency protocols across dies. How many cores you decide to make coherent is largely unrelated to how your die yields work out, as far as I know. Not that it matters either way for this discussion? Whether it's "one server" in that 2U box, or "twenty servers" in that box, you're still shoving in lots of cores and lots of watts to get that density up.
benbenolson 4y ago
That's almost exactly what the Xeon Phi was, both in coprocessor form and in machine form. It included MCDRAM, too, which was a high-bandwidth memory. Very efficient, but lacked sales; people didn't want it. Part of that, I think, was lack of parallelism in applications: in order to fully take advantage of those cores, you need to have a nearly-embarrassingly-parallel problem. Otherwise, you're not going to get the performance that you'd expect (but you'll get power efficiency!). The fact of the matter is, that's not "all anybody wants."
- adgjlsfhk1 4y ago
  also, of you're problem is embarrassingly parallel, you can probably run it on a GPU and it's will be faster.

by booi 4y ago

tadfisher 4y ago

That was Larrabee/Xeon Phi, was it not? Discontinued for lack of sales.

sseagull 4y ago
That’s basically what I thought. However, IIRC they were marketed more towards high-performance computing (with avx-512). They were an uncomfortable middle ground though, between normal CPUs and GPUs. My benchmarks showed that there wasn’t much of an advantage over 20-ish normal xeon cores (for my HPC workloads). (Memory is a little fuzzy - that was 4-6 years ago).
- glowingly 4y ago
  While not exactly what you are looking for, Intel Snow Ridge is a continuation of their Atom-based (next to their line of Core-based) networking processors. 8-24 cores. https://www.intel.com/content/www/us/en/products/details/processors/atom/p.html https://www.intel.com/content/www/us/en/products/details/pro... Though, unless if you 100% need X86, there is the Ampere Altra 128 core Cortex-N1 chip.

astrange 4y ago

That’d be a pretty unbalanced architecture - may use less rack space than 128 servers, but with only one servers’ worth of IO, network, PSUs, it’d be less reliable and maybe not even faster.

booi 4y ago
A single AWS graviton server is roughly 128 cores with, I believe, 2x or 4x 40gbit networking. It’s not crazy really.
Dylan16807 4y ago
One core is probably not pushing more than 100mbit on average. Scaling that much networking up a hundredfold is child's play.

matja 4y ago

AMD's plan with EPYC Zen 4 "Bergamo", with up to 128 Zen 4c cores.

tyrfing 4y ago

128 cores at 30 watts isn't something I've seen anyone planning. What's more likely is 128 cores at 300-400+ watts, and scaling from there is most likely to increase power usage and core counts. Bergamo (AMD), Graviton (AWS), Sierra Forest (Intel), Grace (NVIDIA) are all going for that. 30 watts is low power mobile and "edge" compute.

booi 4y ago
You’re definitely right. I meant 30W per cpu or less which usually means maybe 4-8 cpus per host or ~300W. I did mean to compare it to Graviton and will definitely look at the other contenders in this space.
- tyrfing 4y ago
  Oh OK. Recent server CPUs (Ice Lake) are roughly 8-12W (maybe up to 15W, there are a lot of SKUs) as a baseline. AMD's latest Milan generation brings it down to 3.5W/core, with some closer to 5W; Intel's Sapphire Rapids only goes down to ~ 6W. After M1 and Graviton, there's a big rush for making denser server CPUs, pretty much bifurcating the market. Much more powerful than old Atom cores, but more power-efficient than regular ones, and targeted mostly at hyperscalers. AMD should have a dense variant of Zen 4 out next year, going up to 128 cores and reducing per-core power significantly. Intel will likely have a competitor out in 2024, and AMD might hit 256 cores then, although rumors of things that far out aren't very specific. On the ARM side of things, NVIDIA is launching CPUs like this next year. Qualcomm bought Nuvia, which was working on similar server CPUs, but probably switched focus to PCs. There are some other oddballs like Tenstorrent as well. One interesting part with pushing per-core power so low is that communication between cores starts to be a serious part of total power consumption.

Dylan16807 4y ago

Atoms generally use 3-5 watts per core. So the biggest CPUs they're making are on par with atoms. They keep designing chips that use less and less per core. Why not cram as many cores as possible into a single server? Lower density means more wasted material, and once you go below 2GHz you're not saving very much power any more.

c_o_n_v_e_x 4y ago
> Why not cram as many cores as possible into a single server? Manufacturing yields
- Dylan16807 4y ago
  That's why you limit die size to a certain extent. But that's not a limiting factor on cores per server. You can cram many more 150mm² dies into your server's sockets than you can actually feed with power and cooling and RAM.
  - xxs 4y ago
    A major issue is the cache coherency. If you dont have coherency, effectively you have an architecture that just multiple distinct servers.
    - Dylan16807 4y ago
      You can run coherency protocols across dies. How many cores you decide to make coherent is largely unrelated to how your die yields work out, as far as I know. Not that it matters either way for this discussion? Whether it's "one server" in that 2U box, or "twenty servers" in that box, you're still shoving in lots of cores and lots of watts to get that density up.

benbenolson 4y ago

That's almost exactly what the Xeon Phi was, both in coprocessor form and in machine form. It included MCDRAM, too, which was a high-bandwidth memory. Very efficient, but lacked sales; people didn't want it. Part of that, I think, was lack of parallelism in applications: in order to fully take advantage of those cores, you need to have a nearly-embarrassingly-parallel problem. Otherwise, you're not going to get the performance that you'd expect (but you'll get power efficiency!). The fact of the matter is, that's not "all anybody wants."

adgjlsfhk1 4y ago
also, of you're problem is embarrassingly parallel, you can probably run it on a GPU and it's will be faster.