Complex sentence: Earlier ECU designs were based more on analogue computer circuitry, due to the fact that processing speed there is not an issue; it was not until around 1987 that digital electronics and embedded microprocessor systems became fast enough to process engine parameters in real time.
Split into simpler sentences: Earlier ECU designs were based more on analogue computer circuitry, due to the fact that for analogue circuits processing speed is not an issue. It was not until around 1987 that digital electronics and embedded microprocessor systems became fast enough to process engine parameters in real time.