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> under the hood Surely, we don't have to work with raw quantum electrodynamics when designing an FPGA, even though that's what's going on "under the hood". T

> under the hood Surely, we don't have to work with raw quantum electrodynamics when designing an FPGA, even though that's what's going on "under the hood". Thinking that way, gets me wondering about different layers of abstraction along with the benefits and drawbacks of each. With FPGA programming, what levels of abstraction are available and what simplifying assumptions does each model make? I've got in mind things like Kirchhoff's laws, where we assume perfectly conducting wires, discrete elements, a conservative ambient B field, and essentially DC current over the size of circuit elements. When those assumptions start breaking down, then we can drop down a layer of abstraction.

vvanders 9y ago
I think most HDLs are approaching the diminishing returns of abstraction already. Most of the electrical characteristics are already captured in routing, setup and hold times so while you may not directly interact with them anything more than the most trivial design will be constrained by them. By "under the hood" I was referring to the constraints you have on what you design. In the software space we are mostly constrained by memory(huge), network speed(blazing fast), CPU time(tasks running long normally don't break things). In FPGA/ASIC land those constraints are much, much smaller(kB vs gB) and there are many more(thermals, power, hard cycle requirements, etc).
- slededit 9y ago
  > I think most HDLs are approaching the diminishing returns of abstraction already. System Verilog goes a lot of the way, but there are many good abstractions missing in HDL. Structs were my biggest complaint before System Verilog.
FPGAhacker 9y ago
Don’t know why you are downvoted right now. A major abstraction, absolutely huge, is “Digital.” It’s all analog, and outside of the sanitizing Digital abstraction, it’s not pretty. But the digital abstraction allowed for astronomically complex designs to be implemented.
simcop2387 9y ago
> Surely, we don't have to work with raw quantum electrodynamics when designing an FPGA, even though that's what's going on "under the hood". Probably. But that doesn't mean you might not see the effects of it. I can't find the story/paper at the moment due to too much noise in my searches, but a team of researchers gave some kind of machine learning process (I think genetic programming) an FPGA to treat as a black box to solve some problem. It ended up making a program for the FPGA that didn't work on any other FPGA, and had what should be useless elements in the program that didn't connect anywhere, but without which the whole system wouldn't work properly. So at the least they had some kind of weird effect going on that wouldn't be explained by normal analysis. edit: Found it: https://www.damninteresting.com/on-the-origin-of-circuits/ https://www.damninteresting.com/on-the-origin-of-circuits/

vvanders 9y ago

I think most HDLs are approaching the diminishing returns of abstraction already. Most of the electrical characteristics are already captured in routing, setup and hold times so while you may not directly interact with them anything more than the most trivial design will be constrained by them. By "under the hood" I was referring to the constraints you have on what you design. In the software space we are mostly constrained by memory(huge), network speed(blazing fast), CPU time(tasks running long normally don't break things). In FPGA/ASIC land those constraints are much, much smaller(kB vs gB) and there are many more(thermals, power, hard cycle requirements, etc).

slededit 9y ago
> I think most HDLs are approaching the diminishing returns of abstraction already. System Verilog goes a lot of the way, but there are many good abstractions missing in HDL. Structs were my biggest complaint before System Verilog.

FPGAhacker 9y ago

Don’t know why you are downvoted right now. A major abstraction, absolutely huge, is “Digital.” It’s all analog, and outside of the sanitizing Digital abstraction, it’s not pretty. But the digital abstraction allowed for astronomically complex designs to be implemented.

simcop2387 9y ago

> Surely, we don't have to work with raw quantum electrodynamics when designing an FPGA, even though that's what's going on "under the hood". Probably. But that doesn't mean you might not see the effects of it. I can't find the story/paper at the moment due to too much noise in my searches, but a team of researchers gave some kind of machine learning process (I think genetic programming) an FPGA to treat as a black box to solve some problem. It ended up making a program for the FPGA that didn't work on any other FPGA, and had what should be useless elements in the program that didn't connect anywhere, but without which the whole system wouldn't work properly. So at the least they had some kind of weird effect going on that wouldn't be explained by normal analysis. edit: Found it: https://www.damninteresting.com/on-the-origin-of-circuits/ https://www.damninteresting.com/on-the-origin-of-circuits/