Rohm Co. Ltd. prototyped a nonvolatile CPU and exhibited it at CEATEC Japan 2007. The company prototyped an 8-bit microcomputer and made it nonvolatile by adding ferroelectric memory chips to all of the about 300 registers.
This time, the company demonstrated a breakout game by using a nonvolatile CPU, comparing with the case in which an existing CPU is used.
There are two major merits in nonvolatile CPUs, Rohm said. First, the data remain after the power is cut off. And when the power is being turned on, it is possible to resume quickly operations. The registers of the CPU are nonvolatile. So, it is not necessary to backup the data when the power is being turned off.
The registers, except for the ferroelectric memory chips added to them, are the same as those used in normal 8-bit microcomputers. Therefore, "the processing performance of the CPU does not deteriorate," Rohm said.
In addition, the chip area was hardly increased by making the CPU nonvolatile. It is because ferroelectric memory chips can be formed on a CMOS circuit and because the number of registers per chip is as small as about 300.
As for the second merit, nonvolatile CPUs consume lower amounts of power. Due to the nonvolatile registers, the power can be cut off for processing waiting time of less than 100 ms. In the breakout game demonstrated, the power is cut off for 10 ms when the CPU is not processing data, and the power is on for 4 ms while the CPU is working, Rohm said.
As a result, the power consumption of the CPU can be reduced by about 90%, the company said. Of all the potential applications of the nonvolatile CPU, power consumption can be reduced most when "users' inputs trigger the CPU to work," like the processing of the breakout game. In addition, an application to sequencers is prospective, the company said.