3 ms·

It doesn't matter if it is unrealistic from an engineering perspective, what matters is end-user experience. I've heard technically clueless people complain th

It doesn't matter if it is unrealistic from an engineering perspective, what matters is end-user experience. I've heard technically clueless people complain that their new highend Core-M laptop is slower than their old laptop when they just do work (ie+powerpoint+excel+mail), and they are frustrated. Right then it doesn't matter that the new laptop only weighs half of the old one and still has much better battery life, work is still done mostly at a desk with power nearby.

acqq 12y ago
The top speed is actually the function of the heat generated, and you can generate more when you have better cooling, as simple as that. If some "expert" claimed to the users that by looking at the processor name they can know how fast something is it's the "expert" who isn't.
- m_mueller 12y ago
  > top speed is actually the function of the heat generated That knowledge is rather dated and probably goes back to the Pentium 4 era. Top speed is a function of heat, but also of the process technology and the concurrency available+used. It's best to wrap your head around it by going back to first principles: > The dynamic power consumed by a CPU is approximately proportional to the CPU frequency, and to the square of the CPU voltage: > P = C V^2 f > where C is capacitance, f is frequency, and V is voltage. [1] Capacitance goes down with smaller transistors, voltage and frequency goes up with higher sequential performance given the same architecture. So, by replacing the need for sequential performance with more concurrency (vectorization/multicore/gpu acceleration), the need for power goes down dramatically. Process technology is another big factor. On a related note: Comparing ARM with Core M just using some concurrency using benchmarks is not really comparing Apples to Apples - I expect Core M to have a higher sequential performance - so if you want to have the same performance on ARM, you'll need more concurrency in the software. [1] http://en.wikipedia.org/wiki/CPU_power_dissipation http://en.wikipedia.org/wiki/CPU_power_dissipation
  - seanmcdirmid 12y ago
    I believe you mean parallelism, not concurrency right? Concurrency is dealing (correctly) with more things at the same time, parallelism is doing more things at the same time. The Pentium 4 had a very deep pipeline, which got very hot and wasn't fast compared to its clock. The pentium M went back to more instruction level parallelism via shallower parallel pipes (multi core came later). I don't think ARM is competitive with Intel even with parallel benchmarks; Intel does performance well and doesn't play many tricks with it, ARM's advantage has always been power efficiency and cost.
    - m_mueller 12y ago
      > I believe you mean parallelism, not concurrency right? Concurrency is dealing (correctly) with more things at the same time, parallelism is doing more things at the same time. Yes, parallelism makes more sense in this context. I wanted to express it in a more general way because running multiple programs on different cores at the same time I understand as concurrency, which is also made more efficient by parallel performance rather than sequential - IMO the terms are a little bit fuzzy at times, i.e. it's not that easy to convey the ideas behind parallel programming easily such that there is no ambiguity. Edit: About ARM vs. Core M in benchmarks: After looking at it again, apparently the two are still quite far apart, you were right about their performance numbers: [1] [1] http://www.fool.com/investing/general/2014/09/22/intel-corporations-core-m-significantly-outpaces-a.aspx http://www.fool.com/investing/general/2014/09/22/intel-corpo...
  - Symmetry 12y ago
    I don't think that anybody could reasonably read top speed being a function of heat as top speed only being a function of heat. I wouldn't really associate that idea with the Pentium IV era either since the problem then was that most people weren't thinking about power use at all. Even that equation you gave says that if you increase P you will be able to increase f, though the interplay between f and V means that your increases are sub-linear.
    - m_mueller 12y ago

acqq 12y ago

The top speed is actually the function of the heat generated, and you can generate more when you have better cooling, as simple as that. If some "expert" claimed to the users that by looking at the processor name they can know how fast something is it's the "expert" who isn't.

m_mueller 12y ago
> top speed is actually the function of the heat generated That knowledge is rather dated and probably goes back to the Pentium 4 era. Top speed is a function of heat, but also of the process technology and the concurrency available+used. It's best to wrap your head around it by going back to first principles: > The dynamic power consumed by a CPU is approximately proportional to the CPU frequency, and to the square of the CPU voltage: > P = C V^2 f > where C is capacitance, f is frequency, and V is voltage. [1] Capacitance goes down with smaller transistors, voltage and frequency goes up with higher sequential performance given the same architecture. So, by replacing the need for sequential performance with more concurrency (vectorization/multicore/gpu acceleration), the need for power goes down dramatically. Process technology is another big factor. On a related note: Comparing ARM with Core M just using some concurrency using benchmarks is not really comparing Apples to Apples - I expect Core M to have a higher sequential performance - so if you want to have the same performance on ARM, you'll need more concurrency in the software. [1] http://en.wikipedia.org/wiki/CPU_power_dissipation http://en.wikipedia.org/wiki/CPU_power_dissipation
- seanmcdirmid 12y ago
  I believe you mean parallelism, not concurrency right? Concurrency is dealing (correctly) with more things at the same time, parallelism is doing more things at the same time. The Pentium 4 had a very deep pipeline, which got very hot and wasn't fast compared to its clock. The pentium M went back to more instruction level parallelism via shallower parallel pipes (multi core came later). I don't think ARM is competitive with Intel even with parallel benchmarks; Intel does performance well and doesn't play many tricks with it, ARM's advantage has always been power efficiency and cost.
  - m_mueller 12y ago
    > I believe you mean parallelism, not concurrency right? Concurrency is dealing (correctly) with more things at the same time, parallelism is doing more things at the same time. Yes, parallelism makes more sense in this context. I wanted to express it in a more general way because running multiple programs on different cores at the same time I understand as concurrency, which is also made more efficient by parallel performance rather than sequential - IMO the terms are a little bit fuzzy at times, i.e. it's not that easy to convey the ideas behind parallel programming easily such that there is no ambiguity. Edit: About ARM vs. Core M in benchmarks: After looking at it again, apparently the two are still quite far apart, you were right about their performance numbers: [1] [1] http://www.fool.com/investing/general/2014/09/22/intel-corporations-core-m-significantly-outpaces-a.aspx http://www.fool.com/investing/general/2014/09/22/intel-corpo...
- Symmetry 12y ago
  I don't think that anybody could reasonably read top speed being a function of heat as top speed only being a function of heat. I wouldn't really associate that idea with the Pentium IV era either since the problem then was that most people weren't thinking about power use at all. Even that equation you gave says that if you increase P you will be able to increase f, though the interplay between f and V means that your increases are sub-linear.
  - m_mueller 12y ago