That brings speed advantages, because signals don’t have to travel a long way across the surface of a chip to reach new part of circuit, as they do on an FPGA. When the chip loads a new fold, new circuitry appears in place of the old. Teig estimates that the footprint of a Tabula chip is less than a third of an equivalent FPGA, making it five times cheaper to make, while providing more than double the density of logic and roughly four times the performance.
As with FPGAs, Tabula’s chips contain arrays of many identical basic building blocks that can be programmed to implement any logic function. A memory store on the chip manages the different configurations that the chip cycles through.
Teig’s approach makes sense, says Andre DeHon, who researches reconfigurable hardware at the University of Pennsylvania and has experimented with similar designs himself. Most of the area on an FPGA chip is made up of the wiring needed to connect the elements that do the work, he says. “This new type of design can run faster and avoids parts just sitting there while signals run down long paths.”
Tabula could push reconfigurable silicon to displace conventional, fixed design chips in more places, says DeHon. Making a custom chip requires a guarantee of a few million units, says DeHon, and hence an upfront cost of several million dollars. “It’s a matter of moving the crossover point between the cost of that and the cost of reconfigurable technology.”
Making the reconfigurable approach cheaper could enable even consumer electronics to ship with programmable chips, making it possible for them to be upgraded with new design tweaks. That approach is currently used only in some expensive equipment such as cell-phone base stations. “Sony could say, ‘look at what our competitor Toshiba did’, and upgrade the chips inside their TVs to provide new features,” says Teig. “Getting to digital cameras or TVs is definitely within reach.”
However, Rich Wawzyrniak, who tracks FPGAs and related technology for analyst firm Semico Research, points out that there are limitations to this approach. “The power consumption if these devices is relatively high, and likely too much for a device like a phone,” he says.
But ultimately, says DeHon, reconfigurable chips should morph their design even more often, shifting their workings to match the task in hand in a blend of software and hardware. “These things are really platforms that can run any computation. The grand vision is that we come up with a way for a program’s code to be mapped to the chip when it runs.”