A central theme of last month’s Embedded Processor Forum was the challenge of combining high speed with low power consumption. NeoMagic presented an unusual approach to this problem in its “MiMagic 6” application processor. (For more information on application processors and an overview of the competitive field, see the March 2003 edition of the DSP Insider.)
Most application processors contain DSP coprocessors and/or hard-wired accelerators for video and image processing. Texas Instrument’s OMAP161x family, which contains a DSP coprocessor and video accelerators, is a prime example of this approach. In contrast, MiMagic 6 uses a programmable, highly parallel “Associative Processing Array” (APA) for compute-intensive media processing.
The APA is a 512-row by 160-column array of 1-bit elements. Each element functions both as a processing element and as a 1-bit memory element. Similarly, the entire array can be thought of both as processing engine and as a 10 Kbyte cache. The APA performs operations in a column-wise fashion, with each operation affecting all 512 rows in parallel.
Native APA operations are limited to compare, write, and move. More complicated operations can be constructed from sequences of these basic operations. For example, the APA can perform 16-bit addition using a 48-cycle sequence of operations. Because the APA operates on all 512 rows at once, this 48-cycle sequence translates into a throughput of about ten 16-bit additions per cycle. Consequently, a 100 MHz APA can perform about 2.5 times more 16-bit additions per second than the 204 MHz DSP core in the OMAP161x.
The MiMagic 6 has the potential to achieve good energy efficieny. As illustrated in the preceding example, the MiMagic 6 may be able to save energy by operating at lower clock speeds than competitors like the OMAP161x. In addition, the APA’s tight integration of storage and compute resources may enable it to expend far less energy on memory accesses than competing architectures.
However, the APA will likely be more difficult to program than competing DSP architectures. Fortunately, NeoMagic plans to provide APA software implementations of key functions including MPEG-4, speech compression, and 3D graphics primitives. NeoMagic also plans to provide libraries of basic word-level operations like add and multiply. MiMagic 6 might have performance advantages over its competitors, but its success will likely depend as much on the quality of these libraries as on any hardware superiority.
The MiMagic 6 is expected to begin sampling in the third quarter of 2003. It is priced at $18 in 10,000-unit quantities
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