Within three years, Lyric plans to produce prototypes of a general-purpose probability processor, dubbed GP5, capable of being programmed to take on any statistical task. But Lyric’s first chip, on offer to companies using flash memory in devices and products available to license from this week, is targeted at boosting the efficiency, and ultimately the size, of the solid state flash memory at the heart of portable gadgets like smart phones and tablets.
Flash memory chips store data using areas of charge trapped on their surface. But those clumps are unstable and even small changes in charge can affect the integrity of the stored data. “The difference between a 0 and a 1 is just 100 electrons,” says Vigoda. “Today, one in every 1,000 bits is wrong when it is read out, and in the next generation, the number of errors will approach one bit in every hundred.”
Error-checking chips can correct those errors by drawing on a unique code generated every time data is written to the chip. This checksum can be used to confirm whether the stored data has changed, and makes it possible to calculate which bits have flipped from 1s to 0s or vice versa. This requires the kind of statistical calculation that is difficult to implement in digital logic, says Vigoda, but is ideal for Lyric’s approach.
The firm has been testing a probability chip’s ability to perform error checks with one of the largest flash memory manufacturers. Compared to a typical error-correction chip used today, Lyric’s chip takes up just a 30th of the space and uses a 12th of the energy. “We hope you’ll be walking around with this in your pocket within two years,” says Vigoda.
Error checking is becoming a bottleneck for flash performance and capacity, says Steven Swanson, a computer scientist at University of California, San Diego who studies the performance of flash chips. Hard disks, based on spinning magnetic platters, to a large extent owe their gains in capacity over recent years to advanced error checking being built in, says Swanson. “Compared to [hard disks], we’re still in the early days for flash,” says Swanson, “and it is pretty clear that as flash gets denser, error checking will become more important.”
Although Lyric’s probability chips could connect to conventional electronics, they work in a fundamentally different way, which may create some speed bumps in the minds of engineers, says Swanson. “As a flash engineer, I might find myself wanting to test more of these unusual chips than I would a conventional one to convince myself they are reliable.”