4 ms·

> Fast-forward to today, and I am willing to bet good money that 99% of people who are writing software have almost no clue how a CPU actually works, let alone

> Fast-forward to today, and I am willing to bet good money that 99% of people who are writing software have almost no clue how a CPU actually works, let alone the physics underlying transistor design. I dont fully agree with this. A lot of folks in systems land have mechanical sympathy and deeply think about memory, IO and processors. Things are mostly built upon underlying abstractions. With AI becoming mainstream, some of the abstractions will be pushed down and some might evolve further.

foobarbecue 4y ago
Yeah, definitely not 99%. I'd guess 50%.
- onlyrealcuzzo 4y ago
  > let alone the physics underlying transistor design. You think 50% of SWEs understand the physics of transistor design???
  - foobarbecue 4y ago
    Hm. I mean at the level of "you sandwich some doped semiconductors so that charge at one point controls the current through two other points" I was sort of thinking yes... but I do have a tendency to overestimate what people know and upon further reflection you're right, 50% is way too high. Can haz 30%?
    - tstout 4y ago
      In my opinion likely only 10%
    - BlueTemplar 4y ago
      This % goes waaay down if you're talking actual physics : just how quantum physics result in a semiconductor band gap, and what equations you need to write down to explain the electric behaviour of that sandwich. I can do that, at least for the basic layouts, but my own lack of (clear) understanding would be in the "middle" of the stack : starting up from logic gates, and bottom from scripting programming languages.
mikewarot 4y ago
I understand how stuff works all the way down, but modern CPUs with register renumbering/coloring are mind breaking, then add JIT to things, there are a lot of tricks being used to make things faster that are beyond my stack depth.
- lostmsu 4y ago
  That's mostly the same basic hardware compiled from a large Verilog file, which is sort of like code.
smugma 4y ago
Welsh was a tenured Harvard CA professor until 2010. While there may be some hyperbole, it seems like he’s speaking from some experience of understanding a top tier undergraduate curriculum (and if you don't consider Harvard top tier, he did his PhD at Berkeley before that). My guess is that his bar for “understanding” is higher than yours and the other commenter who suggests 50% of programmers understand CPU design. Even if you took an upper division HW design class 20 years ago, a fair bit has changed and there’s a good chance you've forgotten a bit since then.
- renewedrebecca 4y ago
  Nice argument from authority ya got there.
- dinkumthinkum 4y ago
  He can be tenured all over the place but it doesn’t make his statements true. I think this is too charitable. I think he is clearly trying to make a very sloppy point that “99%” of programmers know nothing about hardware and are just making web apps or something to that effect. I think it’s too charitable to suggest his statement there is some ultra expertise bar he is clawing at. He’s not talking about quantum physics or anything like that; I am sure he is trying to convey that 99% of programmers don’t know surface things like branch prediction or what a super scalar pipeline is. He’s not talking about the intricacies if Sandy Brudge or anything like that. And, he’s wrong. He’s just trying to make a hand-wavy point abs relies on his pedigree to be taken seriously.
  - sgu999 4y ago
    He may be right in saying that 99% of devs don't know what's under, but the 1% remaining is still a larger crowd that the total amount of devs of the 80s... and they are still essential to the industry.
bee_rider 4y ago
I think it depends on how high our threshold for “understands how a CPU actually works” is. I mean sandybridge had 19 pipeline stages, I certainly couldn’t list them all off the top of my head and describe what they did!

foobarbecue 4y ago

Yeah, definitely not 99%. I'd guess 50%.

onlyrealcuzzo 4y ago
> let alone the physics underlying transistor design. You think 50% of SWEs understand the physics of transistor design???
- foobarbecue 4y ago
  Hm. I mean at the level of "you sandwich some doped semiconductors so that charge at one point controls the current through two other points" I was sort of thinking yes... but I do have a tendency to overestimate what people know and upon further reflection you're right, 50% is way too high. Can haz 30%?
  - tstout 4y ago
    In my opinion likely only 10%
  - BlueTemplar 4y ago
    This % goes waaay down if you're talking actual physics : just how quantum physics result in a semiconductor band gap, and what equations you need to write down to explain the electric behaviour of that sandwich. I can do that, at least for the basic layouts, but my own lack of (clear) understanding would be in the "middle" of the stack : starting up from logic gates, and bottom from scripting programming languages.

mikewarot 4y ago

I understand how stuff works all the way down, but modern CPUs with register renumbering/coloring are mind breaking, then add JIT to things, there are a lot of tricks being used to make things faster that are beyond my stack depth.

lostmsu 4y ago
That's mostly the same basic hardware compiled from a large Verilog file, which is sort of like code.

smugma 4y ago

Welsh was a tenured Harvard CA professor until 2010. While there may be some hyperbole, it seems like he’s speaking from some experience of understanding a top tier undergraduate curriculum (and if you don't consider Harvard top tier, he did his PhD at Berkeley before that). My guess is that his bar for “understanding” is higher than yours and the other commenter who suggests 50% of programmers understand CPU design. Even if you took an upper division HW design class 20 years ago, a fair bit has changed and there’s a good chance you've forgotten a bit since then.

renewedrebecca 4y ago
Nice argument from authority ya got there.
dinkumthinkum 4y ago
He can be tenured all over the place but it doesn’t make his statements true. I think this is too charitable. I think he is clearly trying to make a very sloppy point that “99%” of programmers know nothing about hardware and are just making web apps or something to that effect. I think it’s too charitable to suggest his statement there is some ultra expertise bar he is clawing at. He’s not talking about quantum physics or anything like that; I am sure he is trying to convey that 99% of programmers don’t know surface things like branch prediction or what a super scalar pipeline is. He’s not talking about the intricacies if Sandy Brudge or anything like that. And, he’s wrong. He’s just trying to make a hand-wavy point abs relies on his pedigree to be taken seriously.
- sgu999 4y ago
  He may be right in saying that 99% of devs don't know what's under, but the 1% remaining is still a larger crowd that the total amount of devs of the 80s... and they are still essential to the industry.

bee_rider 4y ago

I think it depends on how high our threshold for “understands how a CPU actually works” is. I mean sandybridge had 19 pipeline stages, I certainly couldn’t list them all off the top of my head and describe what they did!