When you think of analog computing, it’s possible you don’t typically think of FPGAs. Sure, a few FPGAs will have specialized analog blocks, but usually they are digital devices. [Bruce Land] — a name well-known to Hackaday — has a post about building a digital differential analyzer using an FPGA and it is essentially an analog computer simulated on the digital fabric of an FPGA.
Whereas traditional analog computers use operational amplifiers to do mathematical integration, on the FPGA [Land] uses digital summers The devices simulate a system of differential equations, which can be nonlinear.
Of course, at heart it is still a digital device in which an 18-bit number format represents quantities. Although theoretically capable of infinite resolution, a real analog system will have some limit based on the noise floor, component variations and measurement uncertainty, so in practice 18 bits is good enough for most purposes. However, [Land] also extends to 27 bits for those applications that need better accuracy. Analog devices are, of course, inherently parallel in the same manner as FPGAs, so that part matches up well.
The example code is in Verilog and there’s even a case where a CPU cooperates with the (simulated) analog computer. At one time, it wasn’t clear that analog computers wouldn’t take over the world. They even made portable ones — if you consider 28 pounds portable. We’ve recently seen a few posts about analog computers. Maybe they’ll make a comeback.