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1、 http:/ Signal Processing Chips reembrace multicore architecturePosted: 03 Nov 2008 Adding cores to a processor to gain a performance boost, while lowering power demand, has become standard practice in the computing and embedded processor industries. While a similar evolution seems inevitable for al
2、l types of high-performance processing, prior experience has made DSP vendors more selective in applying the multicore approach. DSPs are now beginning to reembrace multicore architectures, but mainly for specific applications possessing well-partitioned processing tasks. Perform partitioningA DSP a
3、pplication often comprises only a few highly complex tasks, and system performance improvements depend on hastening task execution, not simply running more tasks. Instead of partitioning at the task level, this system often requires partitioning at the algorithm level. The overall task, such as comp
4、ressing a video stream, must be broken into steps that can run in parallel on separate cores. The task scheduler or OS cannot perform such partitioning; it must come during the software design. Many DSP application developers avoid the multicore approach because of the difficulty of algorithm partit
5、ioning. At the same time, some tasks such as encryption are not suitable to parallelization. Homogenous vs. heterogeneousThis doesnt mean that the multicore approach hasnt been tried with DSPs. PicoChip has long had its picoArray architecture that puts multiple, identical cores together for high-per
6、formance DSP. In most cases, however, multicore design offerings with DSP had not been homogeneoushaving multiple copies of the same core. Instead, they integrated a DSP core with a RISC CPU core. Such heterogeneous DSPs, for instance, have been part of multicore processor designs for a number of ye
7、ars in the handsets and communications industries. The applications these processors targeted readily separate into signal processing tasks for the DSP and control tasks for the RISC CPU, making partitioning more direct. One exception was the Blackfin BF561 dual-core DSP from Analog Devices Inc. The
8、 device used cores that were designed to handle both types of tasks well, so there was no need to partition along task lines. Instead, developers could assign tasks according to their preference to balance the load among the cores. Most developers at the time, however, were inexperienced at partitio
9、ning software and automated tool support was lacking, so the homogeneous multicore DSP was not quickly adopted. The BF561 was an early entrant to the field, said David Katz, ADIs Black fin applications manager, and it was ahead of its time. It has taken a while for people to learn partitioning. He n
10、oted that it has not introduced a homogeneous multicore DSP design since the BF561, although multicore is an important part of our roadmap strategy. Other DSP vendors also view multicore as an inevitable trend for DSPs, for the same reason it was adopted in computing: higher performance at lower pow
11、er. What is now making homogeneous multicore DSP chip designs appear once more is a shift in the performance increases some systems require. In some applications, the need for performance is moving from performing a single task faster to performing more tasks. This shift is simplifying DSP task part
12、itioning, making it more like that of other embedded applications, and DSP vendors are creating products that capitalize on the opportunity. Processing changeWith the rising demand for VoIP and video over IP, media processing has become one such shifting application. A media gateway design, for inst
13、ance, must provide a number of voice, audio and video codecs, and handle multiple independent channels. This application structure is easily partitioned into independent tasks, making it a good fit for multicore DSP designs. The Octasic Vocallo addresses this application space.Vocallo has 15 identic
14、al DSP cores, giving designers considerable flexibility in creating parallel and pipelined architectures that strike the right balance of channel capacity for different installations. Another multicore DSP for communications is Texas Instruments Inc.s TNETV3020 for high-density core networks. What w
15、e are doing now is application-specific multiprocessing, said Ray Simar, manager of multicore solutions at TI. In infrastructure applications youre doing the same tasks, so designs can gravitate to multiple copies of the same processor. The TNETV3020 has six DSP cores, along with a switch fabric and
16、 a variety of serial I/O channels, allowing designers to configure the design for tasks such as channel format conversion. Communications is not the only DSP application changing its character. Audio processing has also grown to require high-performance handling of multiple tasks that are needed for simple partitioning among multiple cores. According to Sujata Neidig, audio DSP product manager at Freescale Semicondu
