Power/Performance Bits: Nov. 4

A system developed by MIT researchers could allow programmers to trade computational accuracy of chips for energy savings; a prototype technology that uses bursts of heat to transmit information over short distances has been developed by a team of engineers at Imperial College London.


Leveraging error-prone chips
MIT researchers reminded that as transistors get smaller, they also grow less reliable, and that while increasing the operating voltage can help, there is a corresponding increase in power consumption. As such, some researchers and hardware manufacturers are exploring the possibility of letting chips botch the occasional computation. The team has devised a system that lets programmers identify sections of code that can tolerate some error, and the system then determines which program instructions to assign to unreliable hardware components, to maximize energy savings while still meeting accuracy requirements.

The Chisel system also contains a tool that helps programmers evaluate precisely how much error their programs can tolerate. For example, if 1% of the pixels in an image are improperly rendered, will the user notice? How about 2%, or 5%? Chisel then simulates the execution of the image-rendering algorithm on unreliable hardware as many times as the programmer requests, with as many different error rates thereby taking the guesswork out determining accuracy requirements.

The researchers said they tested their system on a handful of common image-processing and financial-analysis algorithms, using a range of unreliable-hardware models culled from the research literature. In simulations, the resulting power savings ranged from 9 to 19%.

Using heat to transmit data
Imperial College London researchers have created a low-cost, wireless communications technology that exploits black-body radiation in the infrared heat spectrum, currently used for thermal imaging.

The team stressed that this part of the spectral range is currently underused, and could offer opportunities for the development of a new form of secure communication that could be concealed in background noise, making it harder to intercept or jam using conventional technology.

Interestingly, wireless ship-to-ship communication was introduced by the Royal British Navy in 1867, in which sailors used oil lamps to transmit signals using heat at the visual part of the spectrum. Today, NATO forces still use signal lamps, which emit heat at the near-infrared part of the spectrum, when radio communications has to be silent. However, these communications need to occur at night for them to be effective, and users employ infrared telescopes to receive information.

A potential application for the technology is a key fob for cars that transmits data via bursts of infrared heat, which would be much harder to intercept by criminals.

The prototype technology being developed by the team is the first to have potential civilian applications. It currently consists of a transmitter with miniature incandescent light bulbs that emit bursts of heat in patterns that encode information. This data is picked up by a receiver that filters out external interference to detect the information in the thermal infrared spectrum as it is transmitted and is then decoded by a silicon chip.

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