DSPs tailored for 3G/4G base stations

Tensilica Inc. has launched the ConnX family of DSPs for 3G and 4G SoC designs. The ConnX Baseband Engine for wireless infrastructure features an instruction set with 200 new instructions, a memory bandwidth of 256 bytes per cycle, scalable clustering, and compiler support with a programming model for SIMD vectorization and other DSP functions.

Will Strauss, president of Forward Concepts, said, "Tensilica is seeing that its processor is shipping more as a DSP instead of a RISC, with 350 million cores for DSP on cellphones for audio processing."

However, combining DSP with RISC is not new: Texas Instruments led the way with its highly successful OMAP architecture, followed by Analog Devices with the Blackfin. So what's the differentiator?

According to Chris Rowen, chief technology officer at Tensilica, "OMAP and Blackfin represent one specific compromise between CPU and DSP, but what Xtensa represents is a continuum [of optimization]." This continuum, brought about by the configurability of the Xtensa instruction set, "means you can optimize fully for your application," he said.

At face value, the ConnX announcement can be viewed as a rebranding exercise: The ConnX Baseband Engine joins the proven quad-MAC Vectra LX DSP option, which is now re-branded as the ConnX Vectra Engine. The ConnX Vectra Engine has been used in many customer designs and is an integral part of the re-branded ConnX 545CK standard DSP. The ConnX 545CK was previously known as the Diamond 545CK, which received a BDTIsimMark2000 score of 3820, the highest of all licensable cores evaluated by BDTI.

"Our customers have been customizing Xtensa LX processors for complex DSP functions in the SoC dataplane for years now," stated Jack Guedj, Tensilica's president and CEO. "The majority of our over 350 million cores shipped have performed complex DSP functions. Now, with these pre-designed ConnX DSP modules, our customers will be able to get new next-generation products to market much faster."

Block diagram of ConnX Baseband Engine

However the Baseband Engine brings a lot more to the ConnX party than simple relabeling. Instead, the company made quite a few enhancements that make it very suited to 3G/4G base stations and multimode, multi-standard terminals.

Highlights of the Baseband Engine include 200 additional instructions to handle such OFDM functions as finite input response filters, fast Fourier transforms, FFT and matrix manipulations. Also worth noting is a memory structure for higher bandwidth and throughput, automatic vectorization for ANSI C programs and an eight-way SIMD, three-slot VLIW (very long instruction word) architecture with up to two load/stores plus one MAC and one ALU operation per cycle.

- Patrick Mannion
DSP DesignLine