Acquired startup tips reconfigurable architecture

The Silicon Spice technology came out of work done at MIT by a portion of the company's founding team. The company has an exclusive license from MIT to use the technology.

Though still tight-lipped on some product details, Silicon Spice executives said their new part will be equipped with an instruction-set architecture that can be customized on the fly to match the particular requirements of the running applications. At the heart of the design is a hybrid DSP/RISC chip with an adaptive instruction set that makes it possible to reconfigure the interconnect and the function of a series of basic building blocks, like multipliers and arithmetic logic units (ALUs), on a cycle-by-cycle basis. "This allows us to create a custom path for that particular instruction for that particular cycle," said Ian Eslick, fo under of Silicon Spice. "We can then change the custom instruction dynamically, resulting in higher performance and smaller code space than conventional architectures."

The key patent behind the device lies in the definition of the reconfigurable data path. One challenge is to scale the architecture from an Internet access device to a carrier-class gateway. The company claims the chip is theoretically scalable from 10 to 50,000 channels.

Currently, the device can address up to 240 channels, with an 0.18-micron process on a ball-grid array. "Our approach was to look at the vertical markets and their problems and opportunities," Eslick said. "We then applied reconfiguration where appropriate, to give the required benefits we were looking for in terms of density and software compatibility. The key is the control of the data path. If we rethink how we control and describe computation, we can reduce the overhead in our architecture to get more computing blocks per unit area.

"This ends up being both signal- and packet-processing intensive, with a lot of different moving parts," Eslick continued. "What we've done here is take all this application complexity and built it into a single software-enabled architecture that allows you to take PSTN I/O directly in, and go directly into the backplane on the way out. That results in a tenfold density improvement, allowing us to process up to 240 channels of voice on one part."

Chip interaction

To tie it all together, Silicon Spice devised a multichannel operating system that allows the user to interact with the chip through software, rather than having to go to hardware. The development environment includes a compiler, a debugger and a set of components (hardware and software) "to make it easy to integrate this into the target system," Eslick said.

The Silicon Spice chip has been evaluated at a number of key voice-over-Internet Protocol (VoIP) houses, including Tollbridge Technologies (Santa Clara, Calif.), a leading player in voice-over-b roadband technology. "They've integrated functionality that most do in a more discrete manner," said Jerry Stark, hardware design manager at Tollbridge. "We're a voice gateway, so we're very interested in multiple copies of a DSP algorithm for multichannel applications, and that's what they allow us to do."

Stark was referring to the basic Silicon Spice architecture, which comprises an array of proprietary DSP engines on a chip and an array of supervisory functions in the form of RISC machines. The chip takes DSP algorithms and runs them on the DSP tiles, replicating the algorithm many times. The RISC engines do the scheduling for the DSPs. "In effect," said Stark, "the user doesn't have to be worried about getting multiple copies of the same algorithm running simultaneously. That's what's interesting to us."

Analyst Will Strauss, president of Forward Concepts (Tempe, Ariz.), said the architecture represents "a new class of devices" that he called access communications processors. "We believe that th ese processors will have an even greater impact on the communications market than network processors have had," Strauss said. "Specifically, we believe [they] could be as important to carrier-access and gateway devices as the Pentium was to the PC."

While some compare Silicon Spice's technology to FPGAs, with the inherent difficulties in terms of programming, verification and power dissipation, Ross Mitchell, vice president of packet telephony at Broadcom, disagreed with that analogy.

"It is not in any way, shape or form an FPGA-type solution," Mitchell said. "I hesitate to even use the word reconfigurable in any description of Silicon Spice's technology."

He allowed that the device could be called reconfigurable in one sense, however, "because it does dynamically change the interconnection of the macro processing blocks" — such as ALUs, bit manipulations, media-access controllers, address generation units and so on — "to optimally match the processing element."

The result, said M itchell, is "truly the best of both worlds: programmability, with phenomenal tools and high efficiency."

The device targets the demarcation point between the public switched telephone network (PSTN) and the packet network. This arena is currently dominated by VoIP gateways and remote-access concentrators, replete with general-purpose DSPs, RISC processors, external memories, FPGAs and interconnect devices that adapt the signals on the PSTN to the packet on the packet network. Jobs such devices must handle include aggregation, buffering and packetization on the one side, and encoding and decoding of various compression algorithms, echo cancellation and tone detection on the signal side.

In a market where every watt and every square inch saved can make the difference between a design win or a loss, Broadcom is banking on the projected efficiency in terms of space and power consumption of the Silicon Spice approach.

New weapon

The company, already strong in cable modem and Ethernet s ilicon, gets in Silicon Spice a new weapon with which to jump into gateways and remote-access concentrators supporting high-density voice, fax and data packet transport over WANs at the carrier side of the network.

Broadcom will pair Silicon Spice's silicon and software expertise with its own packet telephony software resources, acquired earlier this year from HotHaus Technologies. The goal is to get to market with production silicon, and hardened software, this year.

"This represents our most strategic transaction to date — definitely our most expensive," said Broadcom's Mitchell. "The architecture is not just another DSP architecture. It embodies RISC technology, high-performance scalar processing, high-performance vector processing, memory technology and reconfigurable data paths within the scalar and vector processors, for unprecedented performance."

Broadcom will issue in aggregate about 5 million shares of its Class A common stock in exchange for all outstanding shares of Silicon Sp ice preferred and common stock. The merger transaction is expected to close within 60 days and will be accounted for as a purchase.

"We're excited about combining forces [with Broadcom] to address this fast-growing market opportunity in carrier access and IP gateways," said Vinod Dham, president and chief executive officer of Silicon Spice, and now a member of Broadcom's management team. Dham, an Intel Corp. veteran, is widely recognized as the father of the Pentium processor.

"With Broadcom's critical mass, we can now extend the architecture to address other DSP-centric markets such as multiport digital subscriber lines and 3G [third-generation] wireless basestations," he said.

But at least one competitor thinks Broadcom may be biting off more than it can chew. Leon Adams, worldwide DSP strategic marketing manager for Texas Instruments Inc. (Houston), a longtime incumbent in the VoIP market, believes the general-purpose-DSP approach offers better development support, software availability and verification tools than the reconfigurable alternatives. Indeed, success for any new processor architecture often lies in the availability of good, flexible software tools for debugging, verification and system integration.

"There's lots between here and the goal line for making cost-effective solutions," said Adams. "The [Silicon Spice] architecture philosophy is interesting, but the 'architecture du jour' won't result ultimately in a cost-effective product."

However, Nancy Goguen, vice president of marketing at Telogy Networks, a VoIP software company acquired by TI, said the merger "does validate TI's strategy of being in the entire portfolio of products that comprise the voice-over-packet market today." She said TI has 80 to 90 percent of the gateway market, and about 30 percent for remote-access servers.

More startups

Nor is Silicon Spice the only startup in this sector. In May, Chameleon Systems Inc. (Sunnyvale, Calif.) introduced its CS2000 family of reconfigurable comms processors, targeting wireless applications.

According to Chuck Fox, president and chief executive officer at Chameleon, Broadcom's purchase of Silicon Spice validates the reconfigurable approach. "No longer will the concept of leveraging reconfigurable adaptive technology for high channel densities be confined to academic circles," Fox said, adding that the 5x valuation premium paid by Broadcom underscores the technology's potential.

Another competitor in the VoIP arena is Malleable Technologies (San Jose, Calif.), which was snapped up in early June by PMC-Sierra Inc. Malleable, a privately held, fabless company, announced in April its Meca DSPs optimized for voice-over-packet applications. Though not a reconfigurable technology like that of Silicon Spice or Chameleon, the Meca architecture was the first to integrate all the DSP and packet-processing functions in a single chip, replacing the 10 or more general-purpose DSPs typically used today.

VxTel Inc. (Fremont, Calif.) also targets VoIP, but "from the carrier side, not the CPE [customer premises equipment] side — that's a clear distinction," said Shri Dodani, president and CEO. Dodani pointed out that "reconfigurable" is not the same as "programmable." The Silicon Spice "FPGA architecture is so reconfigurable that it takes lots of tools to change the configuration," he said. "We have a truly programmable, scalable solution that doesn't need a lot of tools."