Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

RE: Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

permission — Wed, 25 May 2022 19:33:47 GMT

I know microprocessor is an Integrated Circuit. But by definition a circuit comprises of various electrical components like resistors, capacitors while a system comprises of subsystems. How is microprocessor a circuit when it has different sub blocks like registers, ALU block. Please help

RE: Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

181818 — Sun, 04 Apr 2021 15:40:26 GMT

Discuss and Compare FPGA, Microprocessors and GPU

RE: Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

johnbeetem — Fri, 23 Feb 2018 01:04:40 GMT

As Gene said above: interesting comparisons.

Personally, I don't think programming an FPGA in a good hardware-description language (HDL) is inherently more difficult than programming a microprocessor in C. It's just that people are used to programming languages, particularly if they've been programming for years or decades before trying an FPGA. So their initial programming difficulties are long forgotten, while the new challenges of the FPGA's HDL are fresh.

Let's compare C and Verilog, which use similar notations. Verilog is difficult at first, but that's because of Verilog defects rather than HDLs in principle. If you stick to a clean synthesizable subset of Verilog, it's IMO no more difficult than C. The hard part is learning which constructs to avoid.

Now, in what way is an FPGA's HDL like machine language? Well, you do have to be very aware of your registers and memory, which are limited resources. But the same is true if you're programming in C on a small microprocessor. In fact, many people -- including me -- think of C as a portable assembly language that uses high-level language syntax. Thinking of C only as a high-level language gets you into trouble, since while the syntax is high-level, the execution model is machine language. That means that sometimes you run into bugs (like overwriting memory) that can only be understood at the machine-language level. At least with FPGAs you're forced to be aware of this instead of being surprised by hidden traps.

With FPGAs you also need to think about the logic being generated, since there is a limited amount of logic available and you may need to time-multiplex it to get your design to fit in a cheap FPGA. But with C you need to think about algorithm efficiency, and that ends up being a similar amount of work for a good implementation. I suppose a sloppy implementation is less of a penalty with a microprocessor than with an FPGA, but in both cases a good implementation requires skill and effort.

Thinking about the machine language generated by C can make you a better C programmer, just like thinking about the gates and adders generated by an FPGA HDL makes you a better digital designer. But that's true of any technical field: you always can do a better job if you can think one or two levels below the level you normally work at.

JMO/YMMV

RE: Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

DAB — Thu, 22 Feb 2018 20:12:20 GMT

Nice post.

There were many times in my career where I wish we had access to either of these devices.

There were many times when we needed a unique logic circuit to fit into a small area of a circuit board.

At the time, we were implementing bit-slice circuits, which were a good solution at the time, they were large boards and power hogs.

Looking at FPGA and ASIC today, it is like a circuit designers dream come true. Especially in the area where you need to replace an obsolete IC. Just design it up, build a little plug in board, pop out the old chip and insert the new. QED.

DAB

RE: Comparing an FPGA to a Microcontroller, Microprocessor or an ASIC

genebren — Thu, 22 Feb 2018 20:05:53 GMT

Interesting comparisons. You could build either a microcontroller or microprocessor from a FPGA, but you could not build a FPGA from either a microcontroller or microprocessor. ASICs are like one-time-programmable FPGAs, except that ASICs require much more processing (layout, masks ...).

Gene