We consider parallel prefix computation on processors of different and possibly changing speeds. Extending previous works on identical processors, we provide a lower bound for this problem. We introduce a new adaptive algorithm which is based on the on-line recursive coupling of an optimal sequential algorithm and a parallel one, non-optimal but recursive and fine-grain. The coupling relies on a work-stealing scheduling. Its theoretical performance is analysed on p processors of different and changing speeds. It is close to the lower bound both on identical processors and close to the lower bound for processors of changing speeds. Experiments performed on an eight-processor machine confirms this theoretical result.