Many communications systems designers and architects today find themselves facing a growing "gap" between their system requirements and the silicon approaches available to them. They feel constrained by the limitations of these approaches:
- Standard products: not enough flexibility, no ability to differentiate from competitors
- Network processors: performance or feature limitations, difficult programming models
- FPGAs: high production costs, performance limitations, high power consumption
- Standard-cell ASICs: high upfront cost, growing development cycle.
For designs requiring true differentiation, the primary choices are FPGAs (for prototyping and low-volume production) and ASICs (for high-performance and high-volume production). Ideally, the standard-cell ASIC is a perfect solution, if only the limitations could be addressed.
An industry trend now building steam—the move toward Platform-Based Custom Design—is tackling those limitations. An example is LSI Logic's RapidChip offering.
Platform-Based Custom Design relies on the concept of design reuse. No custom chip is entirely custom. In datacom and telecom applications, certain functional blocks are used over and over again, especially blocks that represent industry standards, high-speed Ethernet, advanced memory interfaces, and so forth. Why redesign these blocks, or re-integrate them, for every design, especially when these high-speed circuits pose real design challenges? The same points hold true for processors (MIPS, ARM, DSP), specialty memories (CAM), and other commonly used elements.
Reusable blocks are available in several forms. Along with embedded SRAM, the most universal and complex blocks are physically built onto an unmetallized silicon "slice," which also incorporates a large configurable logic area (transistor fabric) for metal customization. Other reusable blocks are placed into the configurable region. Finally, the customer's unique design is added to the configurable region.
This platform approach has many benefits:
- A faster development cycle
- Reduced engineering costs
- Reduced mask costs (metal only)
- Reduced risk
- A focus on the differentiating aspects of design
- An easy migration path to an all-layer standard-cell ASIC.
Platform-Based Custom Design isn't the answer for every situation. But for those designs where the gap exists (a growing number, as process dimensions shrink, and design complexity and challenges increase), the benefits are hard to beat.