ARM considers kHz clocks for IoT applications

The industry has known for some years that this seemingly metronomic progress wouldn't last for ever; in fact, there is already a perceptible drop in speed. Sooner or later, progress will be stalled simply because of the Laws of Physics. In a keynote address to the recent Hot Chips conference in the US, a leading technologist put a date on it. Robert Colwell, DARPA's deputy director of microelectronics technology, said 2020. In general, the industry has used smaller process nodes to enable chips that run more quickly. This has been particulary evident in the processor market, where clock rates of 3GHz are common; even microcontrollers and fpgas are getting faster. Many observers equate progress with speed, but what if there is progress to be made ata the other end of the scale? What are the prospects for very slow devices? Quite good, according to ARM's chief technology officer Mike Muller in an apparent change of heart from his position three years ago. ARM is looking at sub threshold designs, where the supply voltage is at or less than the voltage required to switch transistors. The work is part of ARM's growing interest in the Internet of Things (IoT). In Muller's view, many devices that will connect to the IoT will need to be powered by energy scavenging, so power consumption will be critical – and sub threshold designs play into this. "We have built a lot of sub threshold and near threshold designs," he said. "Theoretically, it's the right place to be." Amongst the trade offs with sub threshold is clock speed; these parts are likely to run at low tens of kiloHertz rates. The pay back is ultra low power consumption. While ARM isn't about to unveil a sub threshold core in the near future, it is more serious about the approach. "We can do it with a Cortex-M0," Muller contended. In a world predicated on ever faster clock rates, it's a refreshing change to see researchers address the other end of the scale.