DSP Processors, Embodiments and Alternatives: Part II

DSP Processor Embodiments:

The most familiar form of DSP processor is the single chip processor, which is incorporated into a printed circuit board design by the system designer. However, with the widespread proliferation of DSP processors into many kinds of applications, the increasing level of integration in all kinds of DSP products, and the development of new packaging techniques, DSP processors can now be found in many different forms, sometimes masquerading as something else entirely. In this blog, we briefly discuss some of the forms that DSP processors take.

Multichip Modules.

A multi-chip module (MCM) is generically an electronic assembly (such as a package with a number of conductor terminals or “pins”) where multiple integrated circuits (ICs), semiconductor dies and/or other discrete components are integrated, usually onto a unifying substrate, so that in use it is treated as if it were a single component (as though a larger IC).[1] Other terms, such as “hybrid” or Hybrid integrated circuit, also refer to MCMs.

One advantage of this approach is achieving higher packaging density — more circuits per square inch of printed circuit board. This in turn results in increased operating speed and reduced power dissipation. (As multichip module packaging technology advanced, vendors began to offer multichip modules containing DSP processors. )

For example, Texas Instruments sells the 42 dual C40 multichip module (MCM) containing two SMJ320C40 digital signal processors (DSPs) with 128K words × 32 bits (42D) or 256K words × 32 bits (42C) of zero-wait-state SRAMs mapped to each local bus. Global address and data buses with two sets of control signals are routed externally for each processor, allowing external memory to be accessed. The external global bus provides a continuous address reach of 2G words.

It gives a whopping performance of 80 Million Floating-Point Operations Per Second (MFLOPS) With 496-MBps-Burst I/O Rate for 40-MHz Modules.

Multiple Processors on a Chip.

As IC manufacturing technology became more sophisticated, DSP processors now squeeze more features and performance onto a single-chip  processor, and they even combine multiple processors on a single IC. As with multichip modules, multiprocessor chips provide increased performance and reduced power compared with design using multiple, separately packaged processors. However, the selection of multiprocessor chip offerings is limited to only a few devices.

Chip Sets

n a computer system, a chipset is a set of electronic components in an integrated circuit that manages the data flow between the processor, memory and peripherals. It is usually found on the motherboard. Chipsets are usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.

DSP chipsets seemed to follow the move towards processor integration in PC’s. While some manufacturers combine multiple processors on a single chip and others use multichip modules to combine multiple chips into one package, another variation on DSP processor packaging is to divide the DSP into two or more separate packages. This was the approach that Butterfly DSP had taken with their DSP chip set, which consisted of the LH9320 address generator and the LH9124 processor. Dividing the processor into two or more packages may make sense if the processor is very complex and if the number of input/output pins is very large. Splitting functionality into multiple integrated circuits may allow the use of much less expensive IC packages, and thereby provide cost savings. This approach also provides added flexibility allowing the system designer to combine the individual ICs in the configuration best suited for the application. For example, with the Butterfly chip set, multiple address generator chips could be used in conjunction with one processor chip. Finally, chip sets have the potential of providing more I/O pins than individual chips. In the case of the Butterfly chip set, the use of separate address generator and processor chips allowed the processor to have eight 24-bit external data buses, many more provided by more common single-chip processors.

We will continue with DSP cores in a later blog,

Nalin Pithwa

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