The success of ARM vs other RISC CPUs (as was asked in the article)

As to why ARM succeeded so greatly and is still among us as (originally) a RISC CPU, unlike SPARC, MIPS (the list goes on), it was because of its extremely low power requirements - something which wasn't even in the minds of the two designers at the time. However, when they first wired up the first chip and tested it, they noticed after a while that even though it worked, power had not been applied to the power pin.. it ran purely off parasitic power from the data lines.

So, it started to be used in portable, battery-powered devices, like first the Newton, and later all kinds of PDAs and then phones. After a while the yearly number of ARM CPUs sold numbered in the billions, more than any other particular CPU.

"Deeply puzzling, though, was the reading on the multimeter connected in series with the power supply. The needle was at zero: the processor seemed to be consuming no power whatsoever.

As Wilson tells it: “The development board plugged the chip into had a fault: there was no current being sent down the power supply lines at all. The processor was actually running on leakage from the logic circuits. So the low-power big thing that the ARM is most valued for today, the reason that it's on all your mobile phones, was a complete accident."

Wilson had, it turned out, designed a powerful 32-bit processor that consumed no more than a tenth of a Watt."

https://www.theregister.com/on-prem/2012/05/03/arm-creators-...