This is part of IEEE Spectrum’s special report: Winners & Losers VII
In September, when Samsung boasted at a Taipei industry conference that it could make smartphone chips with PC-like performance, a company in Austin, Texas, took an offstage bow.
It was Intrinsity, a small chip designer, that had made the South Korean silicon giant’s claims possible. It had taken the 650-megahertz ARM Cortex-A8—a CPU designed for smartphones, licensed to Samsung by ARM Holdings—and hot-rodded it into a 1-gigahertz processor dubbed Hummingbird. The result could, with Samsung’s backing, power an impressive portion of the next generation of must-have mobile devices. Some even speculate that Apple itself will put Hummingbird in a coming upgrade to its iPhone. It’s all happening very quickly for a start-up that still shares office space with a local magazine and a dentist.
Now that it’s souping up a next-generation Cortex-A9 for an undisclosed partner, Intrinsity is bidding to carve itself a slice of the market for higher-priced smartphones, netbooks, and other portables. And what a market it is! Just as PCs supplanted minicomputers and laptops supplanted PCs, so smartphones and netbooks will replace laptops for many of their uses. Intrinsity and other designers stand to do well for themselves.
“We’re a speed shop that doesn’t go and burn a lot of fuel in the process,” says Intrinsity president and CEO Bob Russo. He and his 99 engineers grease the wheels of a CPU by trimming inefficiencies in the way logic gates are used.
For instance, when those engineers found that the conventional Cortex-A8 used 20 logical steps to perform some simple binary addition functions, they worked out a way to do the same job in four steps, saving computation time. Because this made some regions in the A8 speed up, the transistors in other regions needed to accommodate less traffic and therefore could be shrunk. Smaller transistors mean less power consumption—a critical element in a battery-powered device.
The key to this and many other performance tricks is the type of logic gate Intrinsity uses: 1-of-n domino logic, or NDL, part of its suite of technologies called Fast14 (named after the atomic number of silicon). Russo says NDL can speed up a logical step by 40 to 60 percent. About a fifth of the A8’s functions are benefiting from it, he adds.
Domino logic is a technology typically used in laptops and desktops, where power consumption isn’t nearly as big a deal as it is in a smartphone. Domino logic does most of its work with n-channel metal-oxide semiconductor (NMOS) transistors, which use electrons to carry charge. In contrast, complementary-metal-oxide semiconductor (CMOS) logic uses equal helpings of both NMOS and p-channel metal-oxide semiconductor (PMOS) transistors, which are slower because they juggle holes—the absences of electrons in a crystal lattice. By relying on faster transistors than CMOS logic does, domino logic can speed computation.
“Choosing to invent a funky new logic structure—without the required factor-of-three improvement—is not a sustainable strategy.”
“Seems like a lot of work for a modest improvement in performance.”
—Kenneth R. Foster
“I’d say the company is a winner, but they seem to be relying on trickiness rather than fundamental technological breakthroughs. Is this a lasting solution for a business model?”
—Robert W. Lucky
Today firms such as AMD, IBM, and Intel use domino logic but only in certain circuits. That’s because it consumes more power than CMOS logic, its circuit timing can be more difficult to manage, it’s more sensitive to noise, and it generally requires more time and money to design and implement.
Fast14 puts a twist on domino logic, which lets it use power more economically. One of the most obvious differences is in the way it represents bits. In CMOS logic you can represent the numbers 0 through 3 on two wires as 00, 01, 10, and 11. In traditional “dual-rail” domino logic, you’d need four wires—two for the bits and two for their complements—so you have to switch twice as many wires every time the output changes, wasting power.