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I wrote some speculation about the Esperanto chip a week ago here: https://news.ycombinator.com/item?id=15815920 https://news.ycombinator.com/item?id=15815920

by jabl 9y ago

I wrote some speculation about the Esperanto chip a week ago here: https://news.ycombinator.com/item?id=15815920 https://news.ycombinator.com/item?id=15815920 It does look quite GPU-like, so one wonders what is the "secret sauce" that makes customers willing to pay a premium for it? One advantage could be if the programming model exposes the vector ISA directly without it being hidden behind a SIMT model as in CUDA or OpenCL? Of course, then the question is how to manage all those 4096 minion cores? A mix of MPI and OpenMP? Another advantage could be a single memory domain between the "maxion" and "minion" cores, so no need to transfer memory back and forth between main and GPU memory. Taken together, the programming model could be more like a "standard" one, maybe making it easier to reuse existing code. Then again, nowadays there's probably more people out there familiar with CUDA programming than programming parallel vector supercomputers.

phkahler 9y ago
My impression is that the minion cores will be full RV64GCV but very simple - like rocket but with a vector unit. Also that the whole thing acts like a 4112 core with everyone in the same memory space (did he say that?). So you get 16 cores with awesome performance and 4096 that are slower with normal code but are vector capable. You'll want to make sure the right threads run on the right cores, but otherwise it sounded like a massive multicore CPU. I was happy to see that they've simulated using the minions to do graphics. I've suggested on a number of occasions that lack of a GPU of risk-v could be a problem and that just using a bunch of RV cores with LLVM-pipe might do the job good enough for desktop use. I think they've proved that possibility in simulation. It may not be a gaming machine but it should make a nice desktop machine with solid performance at desktop compositing. Oh, and it'll have teraflops performance for ML and other things. Me, my hobby is ray tracing which really wants to run on general purpose CPUs. Vector instructions can help a bit, but 4096 cores would be spectacular. Also, a decent desktop experience might be had with only 4-8 big cores and 16-64 minions doing GFX. I see potential for a lot of variants of that thing. He said it will be licensable.
- jabl 9y ago
  > My impression is that the minion cores will be full RV64GCV but very simple - like rocket but with a vector unit. Yes, I think they must be very simple. Otherwise they couldn't fit 4096 of them, even on 7 nm. I'm quite sure it's a scalar cpu (er, non-superscalar to make it clear), with a 1 or maybe 2 lane vector unit. > did he say that? Yes, see slide 10 at https://content.riscv.org/wp-content/uploads/2017/12/Tue1136-Industrial-Strength-High-Performance-RISC-V-Processors-for-Energy-Efficient-Computing-Ditzel-Esperanto.pdf https://content.riscv.org/wp-content/uploads/2017/12/Tue1136...

by jabl 9y ago

phkahler 9y ago

My impression is that the minion cores will be full RV64GCV but very simple - like rocket but with a vector unit. Also that the whole thing acts like a 4112 core with everyone in the same memory space (did he say that?). So you get 16 cores with awesome performance and 4096 that are slower with normal code but are vector capable. You'll want to make sure the right threads run on the right cores, but otherwise it sounded like a massive multicore CPU. I was happy to see that they've simulated using the minions to do graphics. I've suggested on a number of occasions that lack of a GPU of risk-v could be a problem and that just using a bunch of RV cores with LLVM-pipe might do the job good enough for desktop use. I think they've proved that possibility in simulation. It may not be a gaming machine but it should make a nice desktop machine with solid performance at desktop compositing. Oh, and it'll have teraflops performance for ML and other things. Me, my hobby is ray tracing which really wants to run on general purpose CPUs. Vector instructions can help a bit, but 4096 cores would be spectacular. Also, a decent desktop experience might be had with only 4-8 big cores and 16-64 minions doing GFX. I see potential for a lot of variants of that thing. He said it will be licensable.

jabl 9y ago
> My impression is that the minion cores will be full RV64GCV but very simple - like rocket but with a vector unit. Yes, I think they must be very simple. Otherwise they couldn't fit 4096 of them, even on 7 nm. I'm quite sure it's a scalar cpu (er, non-superscalar to make it clear), with a 1 or maybe 2 lane vector unit. > did he say that? Yes, see slide 10 at https://content.riscv.org/wp-content/uploads/2017/12/Tue1136-Industrial-Strength-High-Performance-RISC-V-Processors-for-Energy-Efficient-Computing-Ditzel-Esperanto.pdf https://content.riscv.org/wp-content/uploads/2017/12/Tue1136...